The probe is inside the tank. The heating pad is under the tank. Just watching youtube this is how we saw it done. We ran with a heat lamp for a week or two but I kept seeing heat pads are better for ball pythons.
In my head, I'm weighing out as if the same thing were happening for a person. If I'm in a warehouse, the temp for me the floor could be significantly different than the temp at the ceiling, but hey, different species here.