Hi john
Yes thats right - there are lots of fields that are available to the Report Builder in the course completion area including start , enrolment and completion dates - and grade information.
More analysis of dates could be e done in a spreadsheet with calculated fields and grouping etc.
For an example of the fields available for completion go to demo.totaralms.org and login as demoadmin.
Go to Site administration > Reports > Report Builder > Manage reports
Look at an existing report that uses the Course completion as a source and go to the columns tab and add anothyer column to see what columns you can use available columns .
You could also try Add a new Report once you are more familiar with the report builder.
Feel free to use this demo area to try out totaralms functionality in otehr areas.
regards
Craig