Will MySQL reuse deleted ID's when Auto Increment is applied

Will MySQL reuse deleted ID's when Auto Increment is applied

http://dev.mysql.com/doc/refman/5.0/en/example-auto-increment.html
That document I'm reading seems to say something like:
"In this case (when the AUTO_INCREMENT column is part of a multiple-column
index), AUTO_INCREMENT values are reused if you delete the row with the
biggest AUTO_INCREMENT value in any group."
I don't really understand what's being said there. Aren't the values
supposed to be reused automatically?
Thanks in advance...