can anyone answer me this.... on mouse behavior

I have Google this and not been able to find an answer...
I do put my hand in with my mice frequently, to get the babies used to seeing my hand.... that way it is not so "big and scary monster hand"...
I have a couple mice (female moms) that , when my hand is in the cage, many times they push the bedding around to me, like they are trying to bury my hand.
They only started doing this a couple weeks ag. Also to note, this is both of their 2nd litters.
Does anyone know WHY they are trying to bury my hand?
Is it to "keep it and save me for later" or are they like trying to bury me so I "go away"?
LOL, it is not an issue, I was just curious as to the behavior.