In essence you study modules. Those modules are worth a number of credits. Each grade is worth a weighting.
Your GPA is the total of your weighted grades divided by your credits.
http://www.back2college.com/gpa.htm gives a rough guide - just read weighting for "Grade Points"
From the handbook online ...
How do I progress?
To progress from one academic year to another students must pass the stage examination as a wholeby attaining a Grade Point Average (GPA) of 2.0 with no fails in either semester in accordance with the marks and standards document.
For those who do not succeed in passing at the first attempt repeat attempts are available. Examinations for the winter semester take place in January and the
Spring/Summer semester in May/June. Repeat examinations for both semesters take place in the last two weeks of August. Students are allowed to progress to the Spring semester without passing all subjects but will have to repeat the subjects they failed, in the August repeat exams.
They will not be permitted to progress to the second year until the subjects are passed. You should familiarise yourself with the Marks and Standards document which is available in the library and on the student intranet.