Back to the original subject issue:
Using NanoVNA-H_AA_20191018.dfu,
Setting by menu ELECTRICAL DELAY 50n
.. then shell `edelay` reports 50000.000000000
ch>edelay -50
ch>edelay
-50.000000000
At least for this firmware version,
there is a disconnect between negative values by shell and screen menu
Oristo