The A2/B2 inscription in the run out groove has nothing to do with the catalogue number. It is just a pressing plate index number. I've made a few records myself so I might be able to give a little insight into the process.

The first lacquer to be made is given the index A1 (for side A). If the test pressing proves to be satisfactory they go ahead with the production. However if there is something wrong, some minor glitch or something like that, they might have to make a new pressing plate, or even a new lacquer. That second lacquer is given the index number A2. Higher index numbers can also indicate that they have made more than one pressing plate, to be able to manufacture the record in more than one pressing machine (or even in more than one record plant), which is (was) a common practice with records that were expected to sell lots of copies. For example, the original pressings of Never Mind The Bollocks were made from loads of different pressing plates, but they did still contain the same tracks.

http://www.philjens.plus.com/pistols/pistols/pistols_nmtb.htm