[daip] how does uvsub really work?

[Hanno Spreeuw]

Hello, I do not really understand how uvsub works (in default mode). I
understand that one can transform a model of clean components to the uv
plane.
That has to be subtracted from the input uv dataset. How can you subtract
visbilities from each other without getting negative visibility
amplitudes?
Or are they subtracted as complex numbers?
Thanks,
Hanno Spreeuw