Of course registered for GT la. 15 points cannot guarantee whether you can enter into 軒官 or not in the first round. When the first-round result is announced and if lucky enough to enter into 軒官, you can consider again at that time.
My understanding is that: the letter indicates that by accepting the offer, you have to give up 統一派位, not 自行分配 (first round). So I think even after you've registered GT, you can still wait and see the result from 自行分配 as well.
Can any other parent please correct me, if my understanding is wrong?