crpb
One understands that, if one ever reads the admin manual, but who would that do - especially, if you're an experienced admin…? I have to admit, that I made that mistake, too. When going over the settings, I mistook "send quota limit" as Postfix' "max message size", which I intended to set, but which can't be set anywhere in the admin UI.
Btw, after performing the update yesterday, the values for the quotas set in the admin UI and the values returned by grommunio-admin exmdb <mailbox> store get still differ. Setting the unit to GB in admin UI causes grommunio-admin to display MiB - so 6 GB in admin UI result in 6.00 MiB in grommunio-admin.
It does, however, not cause new messages to be rejected, so maybe the admin UI is right after all and gromox-admin needs some work.