The fee parcels (APN)s are formated as a nine digit string with the first three digits representing the book number, the next set of three digits represent the page and block number and the last three digits represent the parcel number.
Include Leading zero's for the book, trailing zero's for the page and block and leading zero's for the parcel.
For example: Book 6, Page 12, Parcel 45, would be entered as 006120045
View a sample of an Assessors Parcel Map