When viewing a course's list of sections, there's no indication as to which of the sections is the one in the currently displayed schedule. This doesn't make too much of a difference if you're only looking at a single class (since you can just find the section number in the block shown on the schedule). However if you consider when a user is looking at many classes, it would become tedious going back and forth to cross reference with the schedule to see which section is selected

An example situation where having the currently displayed section indicated would be useful: consider a user has selected all sections of 5 different courses, each with 4 sections. Their schedule might have ~30 different valid arrangements. They tab through the options until they find one they like, and now they want to de-select all the sections that they are not in. Ideally, they'd be able to scroll down, look at the list of sections for a class, see which one is currently selected, choose the "toggle all sections" option to deselect all sections, and then reselect the section they wanted. They could then scroll down and repeat for their other four courses. Currently however, the user would need to scroll back up and down four or five times, searching for the section numbers on the displayed calendar.

As for how specifically it should be indicated, I'm unsure (but anything would work, really). Maybe highlight it in a slightly darker shade of purple, or bold the text, or put a star to the left of it.