You need to get the probe AND THE TAPE out of the enclosure immediately. Tape should never ever be in a reptile enclosure, as it sticks to your snake a lot better than to the tub.
The probe goes on the outside of the tub sandwiched between a corner of the heat pad and the underside of the tub. Set the thermostat to 90*F, wait for the heat pad to come to its steady-state, use a temperature gun to measure the floor of the tub, and adjust the thermostat up or down as needed.