XL-Desk has four stereo buses (called Mix A, Mix B, Mix C, and Mix D), any of which could be used as a MIX or REC bus as required.
In the age of DAWs, the traditional REC bus is rarely called upon, as signals are usually sent directly to the DAW via the channel direct outs.
XL-Desk lets you decide how you want to use its four stereo buses.
In most cases Mix A (the one equipped with a fader and the ability to use the G Series compressor) will be used as the main MIX bus, with its summed signal being sent back to the DAW for printing.
Any of the other three stereo buses could be used as a subgroup that can be routed to Mix A, for instance after going through a pair of 500 processing slots. And of course, any of the four buses could be used as a record bus in the traditional sense, combining multiple input signals to record onto a stereo pair of tracks, or to separately record stems back to the DAW.