How to perform incomplete RMAN Recovery. We can achive it by using three options.

        until timestamp

        until SCN

        until SEQUENCE#

The following example performs an incomplete recovery until september 16th of 07:00AM
RUN
{
  SET UNTIL TIME ‘Sep 16 2009 07:00:00”;
  # SET UNTIL SCN 1000;       # alternatively, you can specify SCN
  # SET UNTIL SEQUENCE 9923;  # alternatively, you can specify log
sequence number
  RESTORE DATABASE;
  RECOVER DATABASE;
}

Which is best UNTIL Timestamp,SCN or Sequence#

When using ‘until time’, internally, this will be translated
into a SCN and there could be 5 second margin so the resulting SCN could
be slightly different than
expected.

Therefore, the better option is to use ‘until SCN’ as no translation is
required than.

The max you could specify depends on the archivelog files availability.