The traffic of each IP address is measured individually with a 168 hour base in a "sliding window". It means that your IP address traffic counter (under the registered devices tab) shows the last 168 hour, counted back from the current time.
Because of this, there is no "point of reset" of your traffic (as you would expect based on the mobile phone cellular data plan working structure). Your traffic would be zero only if you have no traffic az all for 168 hour.
Only the traffic that leaves the University's network are included in the measurement (eg. public internet sites, google, facebook etc.). The intranet traffic is not counted in it. The direction and the value of the traffic limit can be found in the data plan's description.
Exceeding the limit will result a ban of 168 hour, starting at the time of the event.