Yes, this is right. There's only 95 REAL levels (complete ones, they use at least two sub-levels), but the sub-levels are from 0 to 1FF.
Each sub-levels is basically plain terrain with all your elements such as sprites, blocks, and so it goes on, but a LEVEL is a group of two or more sub-levels that are grouped in a way that it makes it.
EDIT: 96, I didn't counted Yoshi's House.
Nothing worth looking at here.