I’m assuming the wire going into the tank and under the substrate is your uth? Is so, the uth should be under the tank and your thermostat between the uth and the bottom of the tank. You’ll need a temp gun to check the bottom of the tank to make sure it isn’t too hot. Snakes will burrow, so you need to take that into consideration and adjust accordingly. Usually you don’t want the substrate over the uth to be too deep. It’s a great insulator and can cause the uth to overheat.