title_body: Format flash problem on Boox M92
upvoted_answer: The M92 manual says:
  
  Format Flash
  Select Format Flash button in settings, you can format the
  internal flash. Note, after doing this operation all of the data
  in internal flash would be removed
  
  From the internal flash memory, some should be reserved for databases containing the metadata of your ebooks and other content. Even empty databases take up some space.
  2-3Gb out of 4Gb seems excessive for that, but only another Boox M92 user can really give you a comparable figure. As a comparison: My Cybook Odessey HD has 135Mb used from the 1.5Gb internal flash memory.
  On the other hand I think you can expect such a device to complain if flash memory cannot be properly formatted.