Hi @LeoKleym,
Yes, it’s correct to tare between each dose.
There are some improvements you can make to the calibration like adding a luer lock on the end (as it pinches the diameter, making it less likely to bead on the end). You can find some details here: Two changes you can make to your Pioreactor to achieve more accurate doses
In general, calibrations should ideally be done as closely to the production set up as possible. Example: same height of vial / tubing, distance from pumps, pressure, etc. This isn’t always possible, so there’s also some inaccuracy.
Another option is to reduce the DC% (>= 60% is okay I think), which slows the pump down, and will allow for more accuracy (in theory).