I don't know the specific answer, but I would double-check we got the same number of astronauts back down as we sent up.

Totally on point.-

PS. There was a nice movie released 1979 about that :)

IIRC they usually keep an extra 3 months worth of supplies available at the station, to allow for delays to resupply missions. A resupply mission also arrived at the station recently, which would have had additional supplies for them.

If they decide to go with the plan of sending a reduced crew in Crew-9, they'll probably add extra supplies to that too. So, supply wise there shouldn't be any concerns.

> Do we more or less know how many days worth of supplies they have to keep both up there if needed?

Not sure, but a Cygnus resupply mission (NG-21) launched on the 4th of August, so I'm sure they have plenty of supplies.

Supplies aren't an issue - they send up more every couple of months, and just did so a week or two ago.

There is a slight inconvenience in that the ISS has 6 bedrooms and 7 astronauts, so now one of them will be sleeping on the couch for 8 months rather than 8 days.

> sleeping on the couch for 8 months rather than 8 days.

Wonder what that actually translates to, in space

Is there an extra "guest" specially-adapted "zero gravity sleeping bag" or such?

All I read was that the "couch" is a sleeping bag in the Japanese module. I think the real sleeping quarters provide privacy as well as strapping down the occupant as some semblance of gravity.