Current SCN and Soft Limit

My current understanding is this:-

"At any point in time, the Oracle Database calculates a "not to exceed" limit for the SCN a database can have used, based on the number of seconds elapsed since 1988, multiplied by 16,384. This is known as the 'Soft Limit'. If the soft limit is likely to be exceeded in the next SCN increment then Oracle will issue an ORA-0600 error and the process will be cancelled."

Is the soft limit always calculated from the point in 1988 or from the point at which the database was created ?

Are there ANY circumstances under which the current SCN can exceed the soft limit ?  (cloned DB for instance ?)