That number might be a reference to the map image they display on their website.
It may not have an in game api equivalent if it was retrieved via data mining. Maybe contact wowhead to see where they get their numbers from ( they may have generated their own set of numbers for their site after all).
Using the various available map functions I haven't seen any number remotely similar.
However, I can't remember what zone related functions are available pre BFA. Maybe the old zone IDs match the ones on the website but the new ones are just followed on to make the site consistent due to the big map api change.
Edit ... Or as Nimh says
