You can use the Defined Plane pick-mode after scanning an object to remove unwanted points, such as those from the table surface below the scanned object. 
To select and delete all points below a defined plane
 
   
  - Click Point-Cloud tab > Select Panel > Pick Mode > Defined Plane. 
	 
- While viewing the point-cloud from above, select a point, for example: 
		  
 A plane is fitted to the selected point and all points below the plane are selected. 
		   
 
- To delete the selected points, click Point-Cloud tab > Edit panel > Delete Points. 
		  
 
- To exit the pick mode, deselect the Defined Plane button on the ribbon. 
	 
To change the tolerance of the defined plane
 
   
  - Right-click the CAD View while the Defined Plane pick mode is active. 
	 
- If the plane is not fitted high enough to select all the unwanted points, for example: 
		  
 In the 
		  Defined Plane Tolerance dialog, increase the 
		  Defined plane tolerance. 
		 