To delete submissions;
If you want to remove all of the submissions for a form, then on the submissions page for the form select ‘Delete...’ and choose "All" from the dropdown, no need to select individual entries. You’ll get a pop-up double-checking that you want to do this.
To remove all of the submissions for a form before a specific date/time, then on the submissions page for the form, select ‘Delete...’ and choose from the list of available options. You can choose;
If you choose "Custom" you can specify the date and time before which you would like to delete submissions.