Emprex Network Device DVDRW 2016UI - Manual (Page 11)

7
About This Drive
This DVD Writer is also a RPC2 DVD-ROM drive and according to
DVD-Forum, PC chip must be designed into DVD-ROM drives to record
how many times a user has changed the regional code. The first
regional code will depend on the DVD title you play and you are
allowed to modify the regional code 5 times (including the initial one).
After the fifth alteration, the regional code will be locked and only those
DVD titles of the same regional code could be played afterwards, so set
the code carefully.