In the Athlete History and Reports Modules you can set a limit to only show entries for a specific time period or for a specific number of events
In the athlete history, by default all data that is entered for an event will appear (as shown here).
This is the athlete history for a daily review form, and all of the data is shown by default. If you track this data every day for 1 year, a lot of data will appear (with 15 records per page).
Now you can limit the amount of data that shows in the athlete history and for any variables that are graphed by default.