How much should my kitten be eating?

My kitten just turned 12 weeks old yesterday. Currently his feeding schedule looks like this. 7:30-8am, I give 1/8th of a can of wet food. 8:30 I give 1/8 cup of dry food before going to work. I come home around 3pm and give 1/8th-1/4 cup of wet food depending on how hungry he seems. He usually has some dry food left in his bowl. Dinner time is around 8pm and I'll give him another 1/8th can and then I give 1/8th cup of dry food for the night. So he eats about 3/8ths to 1/2 a can of wet food and 1/4 cup of dry food total a day. My issue was that this seems like it's not enough for him due to how active he is but he never finishes the food. So I decided to try a new brand of food today and he ate the entire 1/4 can that I gave him. So now I'm wondering if he just hated the food I gave him earlier and that's why he never finished it or if he just happened to be hungrier and that's why he ate it all. He also never finishes the dry food I give him unless I happened to be out longer than usual so he was hungrier then. He's a very active boy, so I'm just concerned that he's not eating enough. Also I switched from Tiki Cat since that's what the people I adopted him from were feeding him to Fancy Feast.