No mystery is correct Kliska when one does look at history.
Council of Rome, 382ad, 73 books
Synod of Hippo, 393ad, 73 books
Synod of Carthage I, 397ad, 73 books
Synod of Carthage II, 418ad, 73 books
Council of Florence, 1438ad, 73 books
Council of Trent, 1548ad, 73 books
So should one believe the Synod of Hippo or someone 1,100 years later as to what is scripture? Here’s what the synod said:
“Besides the canonical Scriptures, nothing shall be read, in the church under the title of divine writings.’. The canonical books are:—Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Judges, Ruth, the four books of Kings, the two books of Paraleipomena (Chronicles), Job, the Psalms of David, the five books of Solomon, the twelve books of the (Minor) Prophets, Isaiah, Jeremiah, Daniel, Ezekiel, Tobias, Judith, Esther, two books of Esdras, two books of the Maccabees. The books of the New Testament are:—the four Gospels, the Acts of the Apostles, thirteen Epistles of S. Paul, one Epistle of S. Paul to the Hebrews, two Epistles of S. Peter, three Epistles of S. John, the Epistle of S. James, the Epistle of S. Jude, the Revelation of S. John. Concerning the confirmation of this canon, the transmarine Church shall be consulted.” Council of Hippo, Canon 36 (A.D. 393).