manual transmission fluid 2.2

I've done some reseach on this topic and it would seem that in theory a dry fill should be 2,5 liters and a service fill should be 2,2 liters. But members on this forum seem to have gotten away with using only 2 liters. I'm asking this to get a more definitive answer and to see if I can get away...

Hi all, I going to changing the transmission oil fluid in my honda accord 2.2 dtec 58 plate. Its a manual transmission not automatic. I found it a drain plug but i got know idea wheres the filling valve. I unscrewed one bolt on transmission above drain plug but the bolt had a spring, i guess...