I have to respond on this.
This is how burns are created. Snakes will move the bedding away when moving around. And if the top is 90 but the bottom is over 100 due to the insulating substrate, we have a problem now. You need to know the bottom(hottest spot) your snake can get to. And if the top isnt the same temp then THIN out tbe bedding or change bedding's to achieve your temps.