This read-write INTEGER specifies how many addresses are contained in the kxaddrBlock buffer, relevant only when using the read-block operation to bulk-dump multiple MAC addresses at once. An admin's management script sets or reads this to know how many address entries to expect within a single read-block transfer, making bulk address-table dumps more efficient than reading one entry at a time. For example, a script dumping the full address table using read-block(6) operations would check kxaddrBlockSize after each block to know exactly how many addresses were returned in that transfer's kxaddrBlock data.