gp603

I am traveling internationally with wife, lap infant and myself. My wife is on a first class award ticket (on two class plane). I am upgraded to first from coach (confirmed at time of purchase).

It is my understanding that the lap infant ticket price is 10% of the adult ticket price. Should the 10% be taken from my coach ticket price or should the 10% be taken from the price of a full fare first class ticket? The later is what UA did.