Are you asking about what size tire to put on that wheel?

the spec for the wheel rim of 622x15c just tells you that it has a 622mm bead seat diameter and the internal width measured across the rim from bead seat to opposite side bead seat is 15 mm.

You can put any tire that is 622 x something on that rim as long as it fits in the bike frame and isn't narrower than the internal width of the rim.

There are generally accepted sizes that you shouldn't exceed with a tire and rim, but you are unlikely to hit that on most bikes without having frame or brake caliper interference.

On road bikes, most people are running 23 to 28 mm wide tires. Some 32 mm wide. Tires of 622 BSD are more commonly called 700C to add to the confusion.

Oh crap! Got pulled into a 14 year old zombie thread. I hate that. At least I didn't have to read through a 100 posts before getting to the current question which IMO should have been a new topic.

Welcome to BF!