Use the Top tab in the Filter dialog box to define a formula that computes the data that will be included in the view. For example, in the same view discussed above that shows the average Time to Ship for a collection of products, you can decide to only show the Top 15 Products in terms of Sales. Rather then have to define a specific range for Sales (e.g., greater than $100,000) you can define a limit that is relative to the other members in the field. The formula defined on the Top tab is evaluated on the results of the formula on the Condition tab.
Each option on the Top tab is described below:
None - select this option if you do not want to add a limit to the filter. This is the default setting.
By Field - select this option to add a simple limit based on an existing field in the data source. First select the limit range using the first two drop-down lists. For example you can select Top 10 or Bottom 20. Finally select the field and aggregation to base the limit on. So if you wanted to filter based on the Top 10 Sales, select Top and 10 from the first two drop-down lists and then select Sales and SUM from remaining lists.
By Formula - select this option for more advanced filter limits. Select the limit range using the first two drop-down lists (e.g. Top 10 or Bottom 20). Then you can type a custom formula into the text box or open the formula editing dialog box by clicking the button to the right of the text box.