Concerned for safety

[MitsuMike]

I'm guessing on the size, it might actually be smaller, it is smaller than his length... and the thermostat is old and no it can't go higher, could it be that the mat is defective? Although if it was defective would it even heat up? And the mat is the perfect size for the tub he is in, it's just a few inches shorter in length so I move the tub so there can be a cool side (should I just let the whole tub cover the whole mat?).

The heat mat should only be on the cool side. Cool side should have nothing. I can snap a few pics tonight of my little bee in her 6 qt.
And the mat or the thermostat might be messed up, because these mats can get around 140 degrees.