Comics, cards, collector coins and similar kinds have a Grader (or Ungraded for raw items), a Grade, and a Cert number.
Reading a slab label
Choose Scan slab label… on the form and pick a photo of the slab's label. The barcode is read from the photo and the certificate number filled in, with the likely grader when it can tell.
Certificate and serial numbers are searchable, and are listed first in insurance reports.