Each Formlabs resin cartridge is filled with 1 liter of resin. The printer reads the ID chip on the resin cartridge and estimates how much resin remains based on how much has dispensed. When a cartridge has dispensed a liter of resin, the printer determines that the cartridge is empty.

If you have a small amount of resin left in a cartridge, do not pour it into a new cartridge, as this may contaminate the new resin with particulates or small bits of cured resin. Pour the resin into a resin tank that matches the resin cartridge instead. You may wish to unscrew the vent cap on the cartridge and hold the cartridge upside down over the resin tank to drain it completely.