Arachne you have between 2 and 4 Air Casualty. the relevant is keep your fleet size above 0 (counter - losses) nothing more.
the fact there is a separate variable for the losses mean it's not a real reduction of the fleet (contraposed to the reduction army size for losses during the wars) don't think you will see another use of the variable(s) [counter and casualty]
SotterPapaioannou (making a quick calcualtion) 9 before the section, so 11 after yhilin and fheliel bonus.