/For=VolumeName /All - Queries the status of in progress revert operations. If a volume name is specified with the /For operation, ...

%1 %2 [/For=VolumeName] [/All]
    - Queries the status of in progress revert operations.  If a 
      volume name is specified with the /For operation, the progress 
      of a revert of that volume is detailed.  If the /All option is 
      specified, all in-progress reverts are listed.

    Example Usage:  vssadmin Query Reverts /For=E: