REW Hardware IO output limitation

Does REW have a 16 or 17 channel hardware output limitation?
I am trying to measure a room with 22 speakers and can only output up to channel 17 on my RME DigiFace Dante.
I am on macOS. I can see 128 channels in Audio MIDI Setup for the DigiFace.
I suppose I could try to cross-patch the signal in TotalMix, but I'd rather not have to.
Is this limitation built into REW? Is there a possibility of this being changed in the future?
From what I can tell this doesn't change in the Pro version, which I'd gladly buy if it fixed this issue.

REW has assignments for the 16 ATMOS channel names plus a reference. You can change the physical mapping (and/or the labels) of those names to hardware channels using the Output mapping button in the soundcard preferences, so you can access any 16 hardware channels at a time.

Ah. I see that now. Thanks, that's helpful, and apologies as I'm a bit of a newbie using REW. I tend to work in immersive rooms that are more extensive than Atmos. While I can remap the channels and access the IO past 16 channels, which is great, it would be nice to be able to address more than 16 simultaneous outputs.
that being said, this output mapping totally fulfills my need at the moment.
Thanks so much for the response!!

I could increase the channel count that can be mapped, what's a sensible number?