Arun Sirpal looks at how row versioning information gets stored:
I like row versioning– see this link for more details:https://technet.microsoft.com/en-us/library/ms189122(v=sql.105).aspx
If your database is enabled for one of the isolation levels that uses row versioning and a row is updated it will have 14 bytes added to it.
Click through for a demo and explanation.