why only one record-FirstReturnedRecor

Question

S.O.S
The Update method retrieves rows from the table listed in the first mapping before performing an update. The Update then refreshes the row using the value of the UpdatedRowSource property. Any additional rows returned are ignored
which row  refreshes ?!  why not accept all returned rows
which sake is first returned record ?
which mechanism is when I have bacth query update - select ?
please explain me efect first returned record  with small sample