In order to unapprove time, go to Time Tracking > Approved tab and select the time entries you'd like to unapprove by either clicking on the box next to the record and then clicking the "Unapprove" button, or you can click on the three dots next to the time entry under the "Actions" column and select "Unapprove".
Note that when if a time entry trigger a wage increase and you unapprove it, the wage increase will also be removed.
After a time entry has been unapproved, it will move to the Pending tab for you to edit, delete, or reapprove.