Waste volume doesn't equal sample+reagent

[kingy138]

I have very accurately (painstakingly) calibrated all dosing heads, and I'm finding that the accuracy is aligned with my expectation.

The issue I've found is that the waste volume doesn't make any sense, it's ~50ml per measurement too high. Albeit I don't know how much reagent is actually used, it cannot be too much, maybe a few ml.
I know that it washes out the test vessil before it executes measurement, but this is small volume too.

Either way, it doesn't add up.

I've measured the waste volume physically in the container and it's significantly less than what the dosing head thinks should be in the container.

I think this is caused as at the end of each measurement, the test vessil is emptied, the pump continues to run for a period dry, I guess this is to ensure all liquid is removed and clear of the tubes.

Is this normal?
If it's normal and just how the waste dosing head works, then I'm happy, this isn't a complaint, this is me worried I've done something wrong.