Hi,
Best range to go for is this;
Measure on the bottom of the tank under the substrate on the warm side to find the maximum the snake can expose itself to and try and get this to approx 95f.
Adjust the depth of the substrate so that inside the warm end hide the temps sit around 92-94f.
Try and get the cool end hide to be around 80-82f.
That way the snake has a nice range of temps neither too hot nor too cold and can move from place to place without you having to worry.
Does that make sense?
dr del