...out of the $32 dollar reward. When will they give us the rest of the reward? When will they give us the rest of it?

It’s not clear that ‘reward’ is the best word. It’s pretty uncommon. Also ‘out of the $32 reward’ suggests that people know already that there is a $32 reward. Natural things to say are: We were supposed to receive a reward of $32 but got only $8. When will we get the rest? We received only $8 of the $32 we are due. When do we get the other $24?