The most likely answer is that they used trial and error,
on a blank piece of parchment?!?
and seeing as you are tytching up conceptual flaws regarding the map sir voddmort (im sorry…duke!), whats your take on this one:
We’re supposed to believe that during Ron’s first year that Fred and George NEVER checked up on or looked at Ron on the map to see that there was a “Peter Pettigrew” next to or near him? Ever? Recall, F&G “nicked” the map from Filch’s office in THEIR first year, so they’d had it already, and even if Molly didn’t know that they had it, she wouldn’t have said “Keep an eye on your baby brother this year, it’s his first year…”??? Or that they went through two (and a half, almost) years of Ron being there with “Scabbers” that they NEVER ONCE saw Ron next to a “Peter Pettigrew” and if they did, they never asked him who in the world Peter Pettigrew was? As rabble-rousing as the two boys were, we are supposed to believe that they never once checked up on their little brother before they gave the map to Harry?
🙂 Bump 🙂