The 559 is pretty common for MTBs, and most modern bikes.
The other sizes 26x1 3/8 is for some more vintage bikes, old Raleighs, etc. I really think an online vendor should have some really big TEXT to verify a buyer knows what they are buying when they get one of these.
Several sizes have similar issues. I use 20" (451) on one of my bikes, and know to specifically look for that size.