First you'll want to sort the report you're using to have the most recently added records at the top - if you haven't done so already. To do that customize the report and set the sorting to be "sort high to low" by date created. Next, add this report to your dashboard, and within the dashboard customization screen you should see an option for "Rows to Display" for that report section you just added. Set this to 10. This report will now only show the 10 most recently created entries. If you have more than 10 entries in the report, you'll still be able to access them using the pagination controls (Result Pages 1, 2, 3, etc.) below the report.