There are no unified rules by the confederation in Brazil regarding championship stars over club crest. Instead, each club individually celebrates what it wants and how it wants. We'll go over some of the most important and unique cases, while keeping in mind the rest of the 700+ professional clubs in Brazil have some variation of these systems.
Santos FC has 3 elements over it's crest, 2 stars and a crown. The two star represent the two world championships won in 1962 and 1963. The crown is a recent homage to "The King" Pele, the greatest player in club and sport history, who passed away in 2022.
Cruzeiro also has a crown over it's crest but it's not an homage to any "king". Instead, it is commemorative of the year 2003 when the club won a treble, State Championship, Brazilian Cup and Brazilian League. The term for treble in Portuguese is "triple crown", which explains the symbol.
Grêmio has 3 stars on over its crest each of a different color: gold, silver and bronze. Intuitively, the gold star is for the world championships, silver is for the continental championships and bronze for the national championships. Because the stars don't represent a specific title of a specific year, but instead of the fact that they have been champions of that level, stars don't have to be added as more titles are won, they are just incorporated in the symbolism of the already existing stars.
Vasco has 8 stars over its crest and even though visually they're identical, they actually represent very distinct titles. 4 Brazilian Leagues, 1 South American Championship of Champions, 1 Libertadores, 1 Copa Mercosul and 1 "Terra e Mar". Since the year 2000 these stars have always been present on the jersey, mostly over the crest, but on one-off occasions in the inner collar, outer collar or middle of the chest.
Up until 2013 Fluminense had 3 stars over its crest, but confusion of what they stood for lead to their removal. Officially each of the stars signified a sequence of 3 State Championship titles, 1917/18/19, 1936/37/38 and 1983/84/85. However, a portion of the fans believed they signified 3 Brazilian titles, and when Fluminense won the 4th title in 2012 they demanded a 4th star. The club responded to the demands explaining what the stars actually signified and further explained that the addition of a star would require a change in the clubs constitution, so the final decision was to have the stars removed.
The lone star over the Atletico's crest refers to the 1971 Brazilian League title which has a historical importance because it was the first league as we know it today. Atletico won a second league in 2021 and there have been talks about adding a second star, but the internal voting processes to make that a reality have not happened yet. In the 90s certain jerseys had red stars representing Copa Conmebol titles, but they were removed at the end of the decade.
By the 2000's Corinthians had 5 stars over its crest, 4 Brazilian League titles and the 2000 FIFA Club World Cup. In 2011 the club decided to remove the stars from the crest claiming that they expected many more trophies in the future and it would be impossible to pick which ones to represent on the crest or not.
After the clubs glorious year of 2006, Inter had a total of 6 stars on display. The 2 on each ends were for their 4 Brazilian League titles, the central gold star was for their Libertadores title, and, a little counterintuitively, the bigger silver star was for their world title. In 2009 during the clubs centennial year, Inter decided to make some changes to its crest and removed the stars all together.
Between 1981 and 2003 Botafogo had 4 golden stars on its crest representing the consecutive State Championships of 1932/33/34/35. They were removed to give more importance to the lone star in the middle of the crest which represents the planet Venus, which was visible in sky in early mornings when Botafogo's rowing team would start training.
In the beginning of the 1980's Flamengo's first stars were interestingly placed on the side of the crest, they represented 3 consecutive state titles in 3 separate occasions. In 2001 those stars were placed over the crest and 2 more were added, one representing another sequence of 3 consecutive state titles and the other to commemorate the 1981 world title. In 2005 there was a simplification and only the star for the world title remained, which is what we see to this day.
For most of its history Palmeiras had only used stars on its crest occasionally, it wasn't until Rhumell became the kit manufacturer in 1999 that the club added 4 starts representing 4 Brazilian League titles. When the club switched to Diadora in 2003 those stars were removed and Palmeiras wouldn't sport a commemorative star until 2017, when a red star representing the 1951 world title was permanently added. The 8 stars within the crest are a reference to the month of August when the club was founded.
SPFC is the only major club in Brazil to have stars commemorating a sport that isn't soccer. The 3 red stars are commemorative of the 3 World Championships, but the 2 yellow stars are World and Olympic records in triple jump. In the 1952 Olympics and 1955 Panamerican Games, Adhemar da Silva, a Sao Paulo athlete, set new records and brought home the gold. To portray the dimension of the accomplishment, he was brazil's only Olympic gold medalist until 1980.