I could not find settings for changing the formatting of numbers on the Grades page, and I looked at the admin and instructor settings. I do see that the second decimal only displays if a second decimal is available. In other words, if I type only one decimal then only one is visible. Of course I don't have as much control when a student takes a quiz where automatically graded score results in a decimal.
Your question reminds me of a situation I encountered using another LMS that does allow the users to choose the number of decimal places to display. They chose zero and there was a group of assignments where a student's scores were 7, 7, and 7 but the group total was 20! We thought that the system forgot how to add until the instructor shared that they actually awarded 6.5, 6.5, and 6.5 for the three assignments. Those add up to 19.5, which rounds to 20. Perhaps there is wisdom in displaying those extra decimals if they are present.
