Hi,
There is no direct feature to accomplish this but there is a hack and you are gonna love it!
Go into reports and analytics and open a ranked report. Go to the second page and check the url, it should be something like this:
https://sc.omniture.com/sc15/reports/index.html?rp=row%7C50%3Bdetail_depth%7C50&r=Report.MostPopular...
Go to the section 'rp=row%7C50%' of the URL and change the number to to line item you want the reportlet to start from. e.g If you want to start from the 11th line item change it to 'rp=row%7C10%' and press enter. You will see the 11th line item as the first in the report.
Now select 'More' option and click on 'Dashboard' and it will reflect the same in your reportlet as well.
Let me know if this works out for you. Thanks!
Tanmay