Depends on a few factors. I have a 26' Class C that is not well insulated and a few weeks ago we were visiting family and stayed in the MH. The outside temps were in the low 40's and mid 30's at night. In 2 days we went through 1/4 tank of propane (about 1/2 your size) and did a little cooking inside.
You normally don't fill past 80% because, I was told, it allows the propane to expand and contract. Not a scientist so can't argue with the logic.
2017 Grand Design Reflection 303 RLS
1997 GMC Sierra 3500 Dually