Comments/Ratings for a Single Item

There is no such rule.  The maximum allowable number of moves in such a
position is 50, with certain conditions. (See the laws for more details
about the fifty move rule.)

The figure thirteen probably comes from end game studies. If I remember
correctly, King and Rook vs bare King can mate in 13 moves or less
starting from any legal, non-stalemated position.  I belive the
corresponding figures are 8 for King and Queen vs bare King, 14 for King
and 2 Bishops (on opposite colors) vs bare King, and 49 for King, Bishop,
and Knight vs bare King. [Someone please correct me if my memory is
faulty.]

But all the numbers I quoted assume perfect play--the laws do not require
perfect play. (Except in the last case, but truthfully I don't know how to
force mate with a Bishop and Knight in 1000 moves, nor has anyone ever
done it to me.)