Build an Actor Property that shows the count of events where the action matches purchase in the last trailing 7 days.
Then, using Explore, use that Actor Property to build a query that returns users who have had less than 5 purchases and also counts the users who have had more than 5 purchases. This should return 2 separate numbers in a table view.
Build an actor property using the show method that will return a count of events filtered to action that matches purchase. Use time options and select Trailing window from 7 days ago to now and save it. Build a query in Explore that uses table view. This query will require 2 measures. Measure 1 should return a count of unique user actors filtered to user actors with (your actor property created from the first part) that is less than 5. Measure 2 should return a count of unique user actors filtered to user actors with (your actor property created from the first part) that is greater than or equal to 5. Starting 7 days ago and ending now. Split by none.
Actor properties are how you can build permanent segments against your users and then refer to those definitions in any query or with any feature of Scuba.
Note: The numbers and result does not need to be an exact match as the data changes over time. The query construction is what is most important. See images below.
*Click to enlarge*