The issue is that attributes with the "numeric" type can only accept the values 1-9 and no more than 9 characters total.

We need to change the attribute type to Text so that we can enter more than 9 character values.
  1. Go to Accounts Payable > Configuration > Attributes
  2. Highlight Vendor
  3. Change the value in the Data Type column for this attribute
  4. Navigate away from this window to save the changes