I didn't think Routines had Wait options.
look to see if IFTTT supports your switch (TP-Link).
I'm needing something similar but different (wife wake up, say good morning, 30 minutes later, get reminder to take 2nd medication).
Here's the theory to set it up (actual solution may vary):
Name your switch Grinder (for this exercise)
With IFTTT, you'd set it to watch for your Grinder to turn on, and if it allows wait 29 seconds, then send command Grinder turn off
I have SmartThings, so I can probably do this with an SS Routine, or IFTTT. The key challenge is the wait behavior, one which platform provides that mechanism. I suspect IFTTT to cover more of this programmer-centric kind of toolset.