Why is my internet app restricted to 6.86gb

A

AC Question

When i go to settings>applications>internet...under the usage info it currently says 1.81gb/6.86gb used since 4 Dec 2016.

What does this mean? I get 5gb a month with my call plan and it is not related to this. My current data usage is 1gb for this month (new month starts in 5 days). What is this usage referring to? I am concerned that when i get to 6.86gb that my mobile data will stop working. Its obviously a cumulative amount of how much data the internet has used since December last year but why is it counting this here and what will happen when it reaches the limit? All the other apps have similar sayings....help! Thanks