Credit hours are the weighting
A GPA is not an average of grades — it is an average weighted by credit hours. A three-credit course moves your GPA three times as much as a one-credit course, which is why a strong grade in a small elective does less than people expect.
Scales differ between institutions
Ghanaian universities do not all use identical grade-point values or identical class boundaries. Pick your institution's scale before you rely on the number, and check the boundaries against your own handbook — those are what the award is actually decided on.
Cumulative, not semester
Class of degree is decided on the cumulative figure, and the cumulative figure moves more slowly the further into a programme you are. A single strong semester late on shifts it far less than the same semester would have shifted it in year one.