As i written in my first reply Railway has right to unlock such REGRET/WL 1 to facilitate booking if need arises.The CRS has special power to unlock any REGRET status to book ticket(2562 is famous for such booking from BSB for general SL Quota).after booking the status becomes REGRET again.
But two (or three too) different types of REGRET is visible:
First:
...
more... REGRET/WL 1 (rarely opened to book ticket)
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2Nd:
14311 ALA HAZRAT EXP 18-01-2011 BAREILLY ABU ROAD GENERAL
S.No. Date (DD-MM-YYYY) Class - 3A Class -SL
1 18- 1-2011 REGRET/WL 7 WL 79/WL 49
2 20- 1-2011 REGRET/WL 6
This sector has limited quota hence auto REGRET bars any big WL booking.But booking is available against cancellation up to limit .
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3Rd:
and every one know the last type of REGRET of GN quota which can have more than 800=WL limit .But generally around WL 300 mark is a limit in SL for REGRET .