Kh director sample calibration

Made some tests on the calibration process and I've found that the water sample calibration doesn't give me all time same numbers.

water sample tubing is actually 83+16+12 = 111cm

Calibration is performed with Triton T3 400Gramx0.01 Digital scale and also lab tubing scale

Running 3 measurements the results are all the time different, sometimes with 1ml difference

New 4mm tubing and no bubble inside.

Calibrating the reagent with no issue, 4.1ml all time.

Is it normal to have such difference on water sample calibrations ?