an English question

"That said" refers to a previous statement which the following one may qualify or even disagree with. It is short for 'that having been said' and equivalent to starting a new sentence with 'Having said that, ...' It is not considered the best or clearest of English constructions in writing and probably derives from the 'linear thought process' which is acceptable in spoken English but is better avoided in a considered written passage.

May be it is used in the sense of 'as it is said'.