Just heard on BBC6, Marc Riley said: "That was the first on-line show in two thousand ten or, I don't know, twenty-ten".
He - a native speaker (!!!) - doesn't know! .
That expression, I'm sure, wasn't used in it's direct meaning. It was used in the meaning of "in other words" or "as they call it". We have the same example with "I don't know" in Russian. Same translation - same meaning, when being used to enumerate similar things, synonyms or words which have relative meaning.