Your numbers might need a little tweaking but are not too far off. Burrowing can be done for any number of reasons. Is he burrowing on the hot or cold side? He could be burrowing to get to heat, away from heat, doesn't have a hide that suits him, or to get to higher humidity. He could also be doing it just because he wants to make a mess. Check the numbers and the possibilities I have given you and you will figure it out.