1.) Go to 'LearnDash LMS' on left side bar menu -> 'Settings' -> 'Delete User Statistics and User Quiz Attempts'.
Only administrators has access on this page.
2.) You'll find a section at the middle of the page with heading 'User Activity'.
3.) Process of deleting records involves 2 steps:
First Step: Counting all records to be deleted using 'Check Records' button.
Second Step: Deleting all the user activity records from start to selected date using 'Delete' button that also shows a confirmation dialog box before the actual deletion.
This functionality deletes all records of the tables 'learndash_user_activity' and 'learndash_user_activity_meta' from the oldest record to selected date(from date field on the form).
Below are the sample records for both 'learndash_user_activity' and 'learndash_user_activity_meta' tables.
Sample records of 'learndash_user_activity' table.
Sample records of 'learndash_user_activity_meta' table.