Ok to clarify you have six modules which make up your A level Maths grades
C1 C2 C3 and C4 all count towards this. Your grade in P1 as you did not follow on the old course of pure maths but switched to Core counts for nothing.
Your next and final two units are from your applied elements in your case M1 and S1.
If you have retaken any of C1 C2 M1 or S1 then it is the best mark you scored in each unit that goes forward eg. If you scored say 65% in M1 and retook it and got 75% the 75% in M1 will go forward and the 65% will not count towards your grade only the 75%.
So to clear up you need a mark for each of C1 C2 C3 and C4 aswell as your two modules M1 and S1. The best mark you get in an individual module goes forward, not any combination of 6 highest percentages.
God damn thats a long winded way to explain it. Hope you get it now