The problem is that the number of books cannot be something to base it on entirely. For example, when Orthodox say "the book of Daniel" we are including Susanna, the Hymn of the Three Youths, and Bel and the Dragon. Likewise, the Septuagint book of Jeremiah includes Baruch and the Epistle of Jeremiah, although they can be enumerated specifically whenever there is doubt, and are enumerated seperately in certain versions. So when we talk about "Daniel and Jeremiah," are we talking about two books or seven? The answer is "yes." Likewise with Nehemiah and Esdras, we know that there have been several different groupings there in various places in Church history--is it two books, is it three? The same content can be enumerated as one, two or three books, with several different arrangements.