On the Top tab, there are four drop-down menus to configure the filter. With them, you can:

• Choose between the Top and Bottom values
• Specify the number of values to keep (with a Number, a Parameter, or a Set)
• Select the field and aggregation to calculate the Top or Bottom

Here's an example of keeping the five sub-categories with the highest number of Sales:

As always, using a Discrete or a Continuous field on a filter produces different results. It's the same with quick filters.