Yup, those seem pretty decent. If there was a value that appeared more than once, use that; otherwise, try any odd number in that range. If you find the delay each time, you might find one that appears more often than the rest.
Okay, I'll do 5 more and recheck my results
EDIT:
Seconds: Almost always 14 (once 13, 2x 15)
Delay Range: 599 - 615 (I hit 605 3x, 603 2x)