Put black color board on the main video track and stretch it out to 2 minutes or 10 minutes by clicking on the right hand edge and dragging it out to the timecode desired on the timeline.

Go to the title section and click and drag whichever style you want to edit down to the title track. Set it's duration to 1 second and edit the text in it to show 09:59 (for a 10 minute countdown), enlarge that and put it in the center of the screen. Use one of the bold colors for the numerals.

Leave the title track "selected" and go up to the director's chair icon, click, then click on edit, click copy, then paste.

Keep doing this until you fill the timeline title track with one second titles, then go back and double click on each and edit the numerals so the second one is 09:58, the third 09:57 and so on until you have them all edited on down to 00:01.

When you play it you will have a digital countdown by the second. It'll take a while, I just tried it for 5 seconds and it works.

Be sure to save it as a pds file and you can bring it back and add a video presentation to it any time.