Fits The Challenge-Yes, marking of the days, weeks..etc That would be very hard going to work feeling that way. I've been there and done that...hard getting out of bed even when bills are due.
Composition- Good
Background- Okay
My Opinion- I think I'll stick with what I wrote below. A very clever idea [done well] but needed some aged dirt/grafitti or something. I'll also add that the heavy border is a little distracting. Over all it's okay.
I like the idea but I do not like the realization. I think that for that you should have try a dramatic picture , some high contrast, Black and white maybe but not just numbers on a clean wall. It does not , in my oppinion, give the sense of a jail wall.