Asset Transfer REST API Question

Summary: We are using rest api to perform asset transfers, there are some mandatory fields or tags which needs to be assigned. There is one tag P_UNITS_ASSIGNED_TBL, how does this works and affects assets?

Basis my understanding tag P_TRANSACTION_UNITS_TBL reduced and add new lines for no of units, what is the usage of P_UNITS_ASSIGNED_TBL?

Has anyone worked and figured the usage?

Content (please ensure you mask any confidential information): We are using rest api to perform asset transfers, there are some mandatory fields or tags which needs to be assigned. There is one tag