Airbnb (and other calendar-based channels) only allows one room per listing, how does this work with room types on myallocator?

Calendar-based channels work differently from normal channels. For example, only availability can be updated, no rates or any other stay restriction. The way the synchronisation works is with calendar files. You provide the channel with a special calendar file that contains an "appointment" for the days with no availability, thus blocking the dates for bookings. All other dates have no such entry, so they remain bookable.

To import bookings the channel manager in turn needs a calendar file from the channel, which indicate which days have which bookings. In general the information in these files is quite thin, that's why not many details are displayed on Incoming Bookings. To view the full details you need to check with the channel's backoffice.

It's important to note that these channels are not updated immediately when you update the channel manager, as they download the calendar files from us in hourly intervals. Thus a delay is quite possible, but since you usually need to confirm bookings manually this is not such a big problem.

How can multiple units be booked for one room?

This is not possible, since each listing is only for one room and one unit. As soon as one booking is made on such a channel, it won't be bookable again for this day. Other channels (even other calendar-based channels) will of course still be bookable if there is availability. Creating multiple listings for each room is also no solution, since you cannot assign multiple channel listings to a single channel manager room.