title_body: Can't exit the font size screen on the Kindle 10th gen
upvoted_answer: This particular generation of kindle gets frozen quite often. Being on the charger seems to exacerbate the issue.
  So first and foremost if it is plugged in unplug it. Then try to refresh. If it is still frozen hold your power button for 30 seconds it will give you the option to switch off your Kindle , do not remove your finger from The power button just keep holding it until it completely shuts  down ; wait for about 15 seconds or more and then power it back up. This is a hard reboot but it will not remove any of your information off or clear any of your caches or anything like that. It just resets and brings you back to the home screen.
  When you go back into the book it should’ve saved the last setting that you placed which was making your font larger. If it did not save that last change you can try adjusting it again and this time it should allow you to adjust and exit out of the pop-up easily.