650mls is normal for the dry clutch
Very much doubt that the missing 600mls will be sitting in the primary drive casing, you normally have to lean them over when draining to get all the oil out. The reason being that the cases are not drilled at the lowest point which I assume is to keep more oil around the gearbox & less creating drag on the primary drive gears, the plate with the hole in it between the crank & gearbox input shaft is where the oil comes through
Lean the bike over with the screw that is generally mistaken as being to check the level removed & see how much more you get out, there is really only 2 places you could be losing oil, crank seals or into the dry clutch cover.
First place to check would be the clutch seal, pulling the cover over the clutch will tell you whether there has been large amounts of oil in there