I have a repti 500 on the UTH on the outside. and I have a ACCURATE digital thermometer. With the probe under aspen just above glass bottom at the edge of the hide in warm area. It shows a temp of 99-102 just above pad. Put also have a digital laser temp gun and it shows the the aspen at hide edge and just inside hide at 78-81. why is temp so diffeerent? it is 74-76 in cool side and that temp is what I get with digital laser temp gun. what am I doing wrong