Norcolds take on leveling
Leveling:
CAUTION:
The refrigerator is made to operate within 3°off level side-to-side and 6° off level front-to-back (as looking at the front of the refrigerator).
Operating it at more than these limits can cause damage to the cooling system and create a risk of personal injury or property damage. Make sure the vehicle is level before you operate the refrigerator.
Operation during travel:
While the refrigerator should be level when the vehicle is stopped, performance during travel is not usually effected
I prefer Dometics take:
COMFORTABLE TO LIVE IN
Simple --- straight forward --- no math required