To clarify, though I don't know for sure if it is an annotation error or a rule error, but you cannot promote your pawn till after it moves within the promotion zone. Your annotation signifies that you are moving a promoted pawn. Perhaps you meant you were promoting your pawn after capturing on 8a, in which case you would put the plus sign at the end. It makes no difference in this case, but I wanted to make sure you understood correctly.
Anyhow, G*3i