The Filter Lidar Data tool controls the global visibility of lidar returns based on classification and/or return type. Points that have been hidden by the filter will not be used in the analysis tools, with a few exceptions such as applying an elevation fit to a layer in the QC of Lidar Data.
Select the filter Lidar data button from the Lidar Toolbar, or select the Lidar Configuration section of the 
Configuration.
Classifications
Enable and disable the visibility of points based on classification code.
For additional options, such as customizing the classification codes, right-click on the classification section. See Lidar Class Properties for more information.
Return Types to Display
Enable and disable the visibility of points based on the return type. Return types are a descriptive combination of the RETURN_CNT and RETURN_NUM attributes.
Update Return Number/ Count when Deleting Points
This setting will modify the return count (RETURN_CNT) and return number (RETURN_NUM) attributes of points when a point from the same pulse has been marked as deleted.
When a point is undeleted, the original return number and return counts will be restored for the related points.
Pulses Identified by GPS Time and ___
Select Only GPS Time, User Data, Point Source ID or Scanner Channel as the property to determine the point return type along with GPS time.