I found that the lowest range of the BM4070 is 200 uH.
This means that measurements in the 1 uH range can't be very accurate.
The datasheet gives for the 200 uH range an accuracy of 3% +/- 5 digits.
The 3% is fine, but the +/- 5 digits can cause a much larger fault at low readings.
How is the 1.4 uH displayed on the meter?
What might be interesting is to measure the inductance of 10 turns and compare it with the inductance of 20 turns.
The latter inductance must be four times the inductance of 10 turns.