Compute grade from multiple weighted categories.
Category grading comes in two flavours and they give different answers. Total-points grading pools every point into one fraction, so a large category dominates simply by being large. Equal-category grading averages each category's own percentage, so a small quiz set counts as much as a big lab block. Computing both from the same points shows which convention favours you — the gap is often two or three percentage points — and the weakest category is where recovery effort pays most.
Total points
Grade = sum of points earned / sum of points possible x 100
Equal categories
Grade = mean of each category's own percentage, ignoring categories with no points available
The syllabus decides. Where it lists category weights, it is weighted grading; where it lists only point values per assignment, it is total points. If both appear, weights take precedence.
Because nothing has been graded in it yet. Counting it as zero percent would show a failing grade for work that has not happened, which is the most common error in mid-term grade estimates.