Hi Jen

One possibility for this display is that the Grade display type is showing as percentage so someone getting a mark of 60/60 is 100%. You can change this under Course Admin > Gradebook setup > Course Grade settings  select the item and choose Grade display type to Real

Another thing that influences the grade shown is the weighting for the activity . If there are activities that have an additional weighting of 40% and the user has a grade of 100 for these then the course mark would be 100.

The activity weightings are shown under the Gradebook setup 

Regards