so how many zodiac signs would earth c have?

4 At the very least, 8 Likely, 11 Perhaps. 4 Because it’s the Alpha Session, 8 Likely because it became a merged session of 8 Players, 11 Perhaps because Terezi, Karkat and Kanaya are Players from a prior Session that went through with them. You may be able to make a case for Dad being a 12th?