Warning
Make sure you acutally had an initial availablity period.
If you were sitting around in MEM, and able to fly during the initial availability period (plus or minus 4 hrs of the original trip) then you got the 18 hrs of guarantee.
If you weren't there for the whole period, then they assume you never had an initial avialability period - so you were never on long term sub, so you loose ALL of the CR of the trip if they assign you a trip an you don't take it.
Doesn't say that anywhere in the contract, but I lost 22 hrs of pay a couple of years ago because I was in Indy, on hotel standby during my initial availabilty window. They called me for a trip 3 days later, and boom, I lose lots of bucks the 15th of the next month. Suprise!!!!
This is the short version. I'll also post the long version next.