Again, I've never heard, that Bio said anything about the N7 guy not being the protagonist. Somebody must've picked it up from "shinobi" or some "leak" and since then it was BioWare. Can someone link me to the place where it was BioWare, not some news site, not some reddit comment, that said he was not the protagonist?
Back to topic.
Good catch there. It could have some meaning, but it could also be some random constellation of numbers they rolled with a dice. Maybe it will be clarified in the novels or the game itself, that the first number means he's from division Y, the second number that he graduated there, the third and forth that he was in squad X. Who knows.