Case 850 Transmission

I've been checking the trans oil in a Case 850G with the engine not running and the trans cold before use every day. Is this correct or should the engine be running? I have a maintenance manual but not an operators manual and maintenance manual doesn't say anything about checking the oil. We have always checked it first thing in the morning with engine off and its always fine. Today I checked it with the engine running and it was just barely on the stick so the got me wondering.
This...

Case 850 Transmission

Case 850 Transmission