@Lorhian : That's five hundred milliliters, not millimeters (Pg.5)

. It's the exact amount that I give when I donate blood (as I have done for quite a few years). I donate only every three months, twice a month is a lot even if it's during wartime. I was once asked to donate blood plasma though, and that was once a month for half a year. So I guess even this tempo is possible in times like that.