When I am in speedgrader and enter a grade without using the rubric, it only gives me a few grades to choose from but won't let me enter any others. For example, the assignment is worth 24 points and I want to assign 19 points, but the drop down that appears when I click in the grade box only has 20, 21, 18, and 24 on it. If I type in something different in the box, Canvas just puts one of those grades in seemingly at random but won't allow me to post anything different. 

Is there a setting I'm missing?