If you insert a disc marked as region 1 in your drive, it appear a prompt asking you to change region setting of your drive. If you insert another disc, for example region 2, then you receive another prompt to change region. You can change region only 5 times, and then region will become permanent.
To see what region is set righ now your drive, you can use imgburn
See image as reference
In this way you can find what region is set your drive right now and how many changes you still have available