Minecraft wiki entry for stats, associated text: stat
Specifies the command stat whose selector and objective are to be cleared or set. Must be one of:
AffectedBlocks — returns the number of blocks affected by a command
AffectedEntities — returns the number of entities affected by a command
AffectedItems — returns the number of items affected by a command
QueryResult — returns the result of a command query
SuccessCount — returns a command's success count