The Sequence Number of this Revision. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2015 
Syntax
Remarks
 Every Revision in the project will be assigned a consecutive sequence number starting with 1. This number corresponds to the ordering of the Revisions. If a Revision is deleted, subsequent Revisions will update their sequence numbers to maintain a consecutive list.