ZF 220 oil capacity?

[Cuningham]

My ZF220 transmission operating manual states oil capacity is 3 litres but plate on transmission says 4 litres. Can anyone advise which it is?
Do I check the dipstick while engine running in neutral pushed fully in or with it loose or is it checked when stopped again with dipstick in or out?
There seems to be various ways of doing it.

 

[Timeless 2]

Manual says approx 4 litres and check oil level at idle when warmed up. I push the dipstick home and check against the high and low marks.