Raid.Extractor data out of bounds?

[Alsterino]

I am NOT a programmer. I apologize if I am posting in the wrong area, or using the wrong format.
I am using Excel's PowerQuery to reference artifacts.JSON file created with Raid.Extractor. Wonderful tool, but it looks like the artifacts portion lists ID #'s to 4367, while the heroes section shows linked artifacts to those champs with ID #'s well over 5000.
Hero ID 3635 is Ninja... all of the artifacts listed are in active use, but the ID #'s cannot be correlated with gear above. Can anyone help me understand how or why ID's don't match up? I cannot find the relationship of listed gear ID's versus champ gear ID's. Any help would be most appreciated.
artifacts.ZIP