The value you store here is the amount of coins that are being added up, once per frame, to the total (done by incrementing the coin count and decrementing $13CC until 0). This is originally to allow the coin incrementing animation instead of instantly showing the total. This is handled by a code at $008F1D-$008F27.
Usually, $7E:13CC is either #$00 or #$01 (Sprite $7E (unused flying red coin)), but it can be set to other values in order to add up multiple coins at once.
