Gabriel can make 14 more bowls.
I know this because when we make 15 5/8 and 7/10 have a similar denominator, then multiply 28/40 (7/10) by 8, we get 224/40. We can subtract this from 15 25/40 and get 10 1/40. When we turn that into an improper fraction, we get 401/40. Dividing that by 28, we get 14 and a remainder. The remainder does not matter since we cannot make half a bowl.