Update: Seeing a >999 identifier, I was prompted to update the validation and forms to accommodate 0 to 9999 identifiers.
And thus far, sorry for the late reply Slapshot, but I changed my entry to be NA / EU for the time being. If anyone else has 2x accounts, I'll see about adding another column and field in the form :thup:
Edit: Regarding the identifiers cross realms, I found that they're not the same if you have the same Battle.net email.
I was just a special case (lucky me I only have to remember 1 number :3).