When you click on the statistics button you are taken to the graph showing your results. Above the graph you should see a range of dates with a cross button. Click on the cross button and a drop down chart will appear with all the dates you've submitted problems. You should see two grey boxes to the right and left of the drop down chart. Then just click and drag the grey boxes to highlight the specific dates you want to view.
Oh, and yes you probably need to purchase the actual Archer software to use this feature. IMHO the software is probably worth buying, especially if you are unable to sort your data without purchase.
Hope that helps