I am unsure about this context, but it can sometimes refer to a point system.
So if you ate a good piece of cake, you can rate it 10 out of 10 on a scale of 1 to 10 meaning it is really good. so 10/10.
If the cake was bland, it could be 3/10.
Some people use this for appearance of people. A really beautiful person would be a 10.