The Grant number is an unique number assigned per equity grant that cannot be repeated e.g. if “1” is chosen for a certain EE, the system will not allow “1” to be used again.
This is a safeguard as the number assigned will serve as an identifier when searching and importing data.
A grant number can certainly be relevant for more than one EE. However, the employee wouldn't have this grant number value more than once.
HC Article: https://help.hibob.com/hc/en-us/articles/4510491610001-Set-up-Equity-tables#how-to-set-up-equity-tables-manually-per-individual-employee--0-2