According to this spec sheet, there's only 2 times (Ton & Toff):
http://www.alliedelec.com/Images/Pro...M/793-8510.PDF
Ton is the length of time it's on & Toff the length of time it's off.
Then repeat as long as "U" is high.

But this sheet says that it's a "twin timer":
http://search.digikey.com/scripts/Dk...me=646-1190-ND

I would be very leery of replacing it unless/until you understand its
function exactly!

Bob