Scheduling interprets "scheduled to depart w/in 45 minutes after the end of your standby shift" to apply only at the time they assign the flight. So in effect if they really need you, your nominally 8 hour standby shift is only limited by 117 duty restrictions. You can and will sit another 4 hours and bang out a 2 hour midnight run with manual closeouts on both ends.

Sadly, if you are stuck on reserve and too senior to get called off RAP and there's no open time to proffer because there's nowhere near enough flying to go around here, standby is the only way to get stick time/possibly an overnight.