To avoid showing too little activities, you can hide events if a minimum is not met by setting a number in the "Minimum events to display" field.
To avoid showing old activities, you can hide events that are older than a certain time period:
Toggle ON the "Hide events that are older than" option.
Configure the value and time unit (minutes or hours).
Note on Numbers Algorithm
When no Hide events older than or Minimum events to display is set, we count the current day's events (since beginning of the day UTC time).