Team Chemistries count

Does anyone know how the team chem are calculated. I know you have to have them in their assigned positions. 

I have purchased a lot of GA chemistries. The problem is when I remove my SS (Dan Jackson) who is already a GA player my count goes down 4 players. So I have to leave him as my 2nd string to keep 4 players for the total even tho I have better SS. 

It would be nice to see how all chem are calculated. I have 6 players who are 3-4 defense but I have 30 players total. That’s cool, just wanna know how it works.