So if the X I'm looking at has 39k on the clock and has an 08/07 date on the VIN sticker, does that mean it's still under original warranty and then the CPO will start once I hit 50k? Or will the CPO start as soon as I buy the truck, if I do?

Also, it was a lease for a year and then someone bought it at 22k miles and owned it for a year and a half. Did the second owner (first buyer) still have the factory warranty or was it CPO'd back then?

It's a bit unclear how this works.

Again, OP, sorry to hijack.