Gas absorbsant refrigerators that are in campers are sensitive to level orientation only side-to-side of the refrigerator. Since they are usually installed on a side wall of the camper, the camper should be leveled fore and aft. Side to side level doesn't matter.
The way to tell if the level is close enough is to open the back of the refrigerator and check that each of the zig-zag pipes slope upward somewhat. Most refrigerators can be quite a bit out of level before any damage will be done. But if things get grossly out of level such that the gasses cannot flow upward through the zig-zag pipes expensive damage can occur if you leave the propane
heat going. I can vouch for that!!
So, buy some stick-on trailer levels. First level the trailer to the refrigerator. Then stick the stick-on levels on a convenient to see spot on the outside of the trailer. They will be very close to parallel with the belly band. If not, check the refrigerator level again.