You have demonstrated that you don't actually understand how the A* award in mathematics GCE is awarded ITIQ. It is not necessary to obtain an average of 90 or obtain 90 or more on both C3 and C4. In fact it is possible to get an A* with a mean mark of 80 and 80 in either C3 or C4. I have seen various university offers that have specified requirements on particular modules. Failure to attain 90 (or even 95 UMS) on individual modules may mean the student is not selected for interview, not given an offer or (in the case of Cambridge) left swimming in the Winter Pool.