Data type: PtypInteger32 ([MS-OXCDATA] section 2.11.1)

The PidTagInstanceNum property ([MS-OXPROPS] section 2.744) is an identifier for a single instance of a row in the table. When a RopGetCollapseState ROP request ([MS-OXCROPS] section is sent, the client passes this property value in the RowInstanceNumber field to specify a cursor to store. When this property is included in the column set, the server sets it to a different value for each row that is an instance of the same underlying data.