The rules:
Mathematics - Compulsory Units: C1-4; Possible Application Units: D1D2, M1M2, S1S2, D1M1, D1S1, M1D1.
A* - gain a total of 180 UMS in C3 & C4, and 480 UMS for all six units taken.
Further Maths - Compulsory Units: FP1, FP2/3; Possible Application Units: The remaining AS unit(s), the remaining FP unit, and other A2 units built consecutively (i.e. If you have taken M1, you cannot take M3 without M2)
A* - gain a total of 270 UMS in the BEST THREE A2 units (note this does not have to include FP2 or FP3) and 480 UMS for all six units taken.
F. A. Maths - Compulsory Units: None; Possible Application Units: All units not previously cashed in.
A* - gain a total of 270 UMS in the BEST THREE A2 units and 480 UMS for all six units taken.
AS Units: C1, C2, D1, FP1, M1, S1
A2 Units: C3-4, D2, FP2-3, M2-5, S2-4