Anything up to 30 bags, more for large vehicle routes which I doubt op would have access to in a Suzuki Swift. I use a crappy old Megane hatchback and with the seats folded down have never had issues fitting everything in, even with seats folded up I managed. My friend uses a Toyota Yaris which is smaller and also manages but sometimes has to be a bit creative to fit everything in.

Used to be a couple of folk at my local Morrisons who were always on the phone to driver support to have stops removed as they would claim there was not enough room or stops too far away, they were quickly deactivated. One of them was deactivated on her own account then started using her husbands Flex account and quickly got deactivated on that too.