[Therion] Question about "grid" command

[Benedikt Hallinger]

Good morning,
while debugging https://github.com/hbeni/therionsurface2survex/issues/1 
i stumbled upon a format question i did not give tought until yesterday.

With the "grid" command you specify coordinate origin and size of a 
surface grid:
   grid <origin x> <origin y> <x spacing> <y spacing> <x count> <y count>


Until now i assumed that:

a) these data has to be all positive.
But i'm not sure... origin may surely get negative (like in wgs89 and 
for example western and southern of the 0-meridian/equator)
And also stepsize - might it get negative too (esp. with flipped grids 
maybe)?

b) the spacing might only be integer numbers, not floats
Is this true? I just got an example with not-round stepsize.