The vertical extent of a space represents the space vertically from the base to the upper limit. Sometimes, you need to redefine the vertical extent of a space. 
This can occur for the following reasons: 
- The upper limit of the space is specified incorrectly. 
 
- The limit offset of the space is specified incorrectly. 
 
- The space is referencing the wrong base level. 
 
- The base offset of the space is specified incorrectly. 
 
- The volume of the space is needs to be redefined. 
 
-  A change occurred in the specification.