chart with some missing points

Have a look at the attached.

It is a combination bar and xy-scatter.
Bar chart provides students ID and xy the duration lines.

You will need to change the layout of your data, via formula, into usable values to provide a line that breaks.

Notice that the lines art very short as minutes in terms of days in not a lot.
1440 minutes per day, student usage on average is 31.

I have added a record so you can see the effect of a student being logged on all day.