[ccp4bb] mtz for zanuda - which symmetry?

[Frank von Delft]

Hi -

For Zanuda, the mtz input it wants:  what spacegroup are the data meant 
to be merged to?  The highest possible, potentially twinned? Or the 
lowest possible?

I've looked reasonably hard (>10min on the manuals and The Google), and 
the answer did not leap out at me at all.  Even though it seems a rather 
crucial question - or is it not, in which case, why not, what am I missing?

phx