the block walls sit on concrete footings all the way around. The ground under the gravel beneath the slab slopes toward the back (shallow at the front and deep towards the back) on top of that sloped dirt is gravel (mixed rock) that Is leveled to approximately 4in below the top of the top layer of block. So I’d image there was more gravel needed in the rear of the slab to backfill in Order to completely level the rock
