levo - 9:31 pm on Sep 3, 2012 (gmt 0)
If a report requires calculation on more than 250,000 visits, we select a statistically random sample of 250,000 visits and estimate the report results based on that data. This makes reports faster to load, and our testing indicates that the data returned is highly accurate.
To use the new report calculation control, click the new icon (square cube graphic) in the upper right of your report when you see a message that your report was generated with a percentage of your visits. Then you can drag the slider to your desired number of visits: we will automatically recalculate your report and remember this number for all reports until you log out.