I see what you mean but thats riduculous, and I think I can only see it because I know what it is! There is no way anyone even slightly iffy sight could see it. An experimental test subject 'Mrs Tumbleweed' who has the eyesight of a condor could get 3 of the digits after a couple of guesses.
When I phoned up to get the PIN, they actually had a recorded message that said 'if you have received a pin notification and you cant read it, press x' or words to that effect so must be quite a few people hitting this problem.