You'll probably get away with a regex of "a + followed by 25 numbers, spaces, or commas, then a #". The OCR may not pick up the spaces, or the AI might kick in and decide "all commas have spaces after" and pop in an extra couple, so you could make the range 22-27. So: \+[\d ,]{22,27}#.
You could get fancier, but that's probably complex enough given that you're unlikely to have anything similar on screen!