While student grades could be appearing incorrectly in the gradebook for a number of reasons the most common issues we see can be fixed with the following steps.
Enter the gradebook of the course with oddly low grades.
Select the Grades option from the Secondary Navigation.
Select the Gradebook Setup option from the Tertiary Navigation.
Locate the name of your course on the table of grade items and expand the Edit menu for it.
Click the Edit Settings option.
Under Grade Category ensure Exclude empty grades is checked.
WARNING: Doing this will may also cause grade to appear higher than expected unless you manually enter Zeros for missed assignments.
Scroll to the bottom of the page.
Click the Save changes button.
For EACH category locate the category title and expand the associated Edit menu.
Click the Edit Settings option.
Under Grade Category ensure Exclude empty grades is checked.
WARNING: Doing this will may also cause grade to appear higher than expected unless you manually enter Zeros for missed assignments.
Scroll to the bottom of the page.
Click the Save changes button.
Repeat for each category.