Assign a max score to our testDouble tap on the column's header > Grade type > Max score 20
Add a simple calculation
We will now add a new column > Calculation > Average
Tap on the 'Test' column header to add it to our calculation
Tap now on Column (properties) and set the grade type to 'Text grades A to F'. This is where you decide how the result of the calculation will look like. A grade type 'From 0 to 100' would show the result as a percent.
And this will be the result
Create your own text grades
Convert a score into a percentage