I aim for 23l into the fermenter, what I find is with wort contraction due to cooling, and the losses due to not wanting to get trub into the fermenter is that I end up with a fair loss as well as the evaporation losses.
Everybodys system will likely be different and what I tried to do was set out as basis how my system works so that other brewers could adjust to suit their system.
Barry Cranston brewed most of the lagers and he took my recipe and fed it into Beersmith without problem.
Hope it works out OK for you
Cheers
Peter