One note on VendorNum …
All DMT processes use the VendorID. Trying to set the VendorNum during initial importing of Vendors, does nothing. The VendorNum is assigned sequentially. If the DMT file you upload has a vendor number field, which is totally ignored. Any other imports you do (like PO Header), should include the VendorID and NOT the VendorNum.
Side note, as a hack to setting the starting number. Just create as many new vendors as you need to get that counter up to 89999. then delete all of them except for the one that made 89999. Any newly created vendors would start at 90000. Delete 89999 after 900000 is created.
“Just be cause you can do something, doesn’t mean you should do it.”