Too Many AWR Intervals?

Any idea why I have 3 AWR sampling Intervals? I didn't know you could have 3.  Seems like 2 too many.

SQL> select extract( day from snap_interval) *24*60+

  2         extract( hour from snap_interval) *60+

  3         extract( minute from snap_interval ) "Snapshot Interval",

  4         extract( day from retention) *24*60+

  5         extract( hour from retention) *60+

  6         extract( minute from retention ) "Retention Interval"

  7    from dba_hist_wr_control

  8  /

Snapshot Interval Retention Interval

----------------- ------------------

               60              11520

               15              86400

               15              43200 

Thanks!

-Ken