Sometime you may see the connection time is more than 15 seconds although the max connection time is only 3 seconds.
I had asked my hosting provider, and was told that it's scheduled network maintenance (??).
It often lasts about 1 or 2 hours.
Here's the message from HP:
It's possible that the delay you experienced was due to the planned network maintenance that took place...
As SetCronJob calculates price by connection time and output length, if the connection time is more than 15 seconds, it will be decreased by 15. For example, you see the connection time is 15.2 seconds and output length is 0.9 KB, the cost will be ceiling(15.2 - 15) + ceiling(0.9) = 2 (*$0.00001).
This will be considered a downtime, and SetCronJob's daemon will not work when this problem occured although you can access SetCronJob normally. All missing jobs will be executed later.