OK, that explains it, since you were either done via a trolley or one of the portable wands attached to a tablet + printer, I assumed you were processed via the usual check-in desks. The usual BA label format is shown here, you will see the 0125 below the BA nnnnnn number. And that's how it's encoded, but most people would read it as BA nnnnnn. But the mobile units come out slightly differently with the 0125 numbering prominent. The screens are set up for the check-in desk version, which would be 99% of situations.