If the tank is full to the line- it holds about 200ml. You can not get all 200 ml out of the tank, because you need at least as much resin as it takes to fully wet the tank floor after each wiper operation.
The Preform estimate is accurate as to actual part volume… however, a certain amount of resin is lost with each print run- some coats the parts, and the Platform has some coating it. The platform eats about the same amount of uncured resin with each run, whether one tiny part or a bunch of really big ones… but the amount coating the parts varies with the volume of the parts… I figure rough loss estimate of about 5% of the print run volume.
With your part at 105ml- figure your actual resin use will be 110.25ml- that means your 7 parts used up 772ml of resin. If you ran an 8th part you would be up to 882mls That would leave you about 118 ml in the tank- which is pretty close to the minimum you can get away with having in the tank.
You should be able to successfully run an 8th part.
100 ml of your first cartridge of any material effectively can not be printed- its needed to wet the tank.
But when you stick the next cartridge of the same material in- you already have 100ml from the last cartridge in there- so you should get closer to the full liter of parts with allowance for loss.
If you buy a new tank, and pour the resin from the burned tank into the new tank- again, you have the initial resin already in and a new cartridge should net you closer to 1 litre of parts.