This seems absurd, but it doesn’t seem like the kind of thing somebody would just make up. What’s the story here?
It is historically incorrect, but we can make a few general inferences about what the author is referring to:
(1) He is probably Eastern Orthodox, because some branches of Orthodoxy have a larger Canon than the Catholic Church and the Orthodox are more likely to make historical arguments than Protestants are.
(2) He is probably referring to the Council of Hippo, which occurred in 393 A.D.
(3) The text of its decision, according to a Catholic Answers tract, is this: “But the canonical scriptures are as follows: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua the Son of Nun, Judges, Ruth, the Kings, four books, the Chronicles, two books, Job, the Psalter, the five books of Solomon [Proverbs, Ecclesiastes, Song of Songs, Wisdom, and a portion of the Psalms], the twelve books of the prophets, Isaiah, Jeremiah, Daniel, Ezekiel, Tobit, Judith, Esther, Ezra, two books, Maccabees, two books . . .” (Canon 36 [A.D. 393])."
That totals up to 44 books by my count. Add the 27 of the New Testament and you get 71. It is missing Lamentations and Baruch, which were often considered chapters of Jeremiah at that time, which brings us to 73, the number in the Catholic canon, but well short of the 78 the author claims. (Maybe there’s something more that the “…” is covering up?) So I don’t know where he gets the number 78.
(4) The “Roman Catholic schism” probably refers either to the schism of 1054, in which we Catholics say the Orthodox broke away, but some Orthodox argue that it’s the other way around, or the Photian Schism in the ninth century, in which the Pope excommunicated Bishop Photius, whom the Orthodox consider a saint and to which many of them trace the permanent separation of the two Churches.
(5) There may be a confusion about the two books of Ezra mentioned in the text of the Council. They refer to Ezra and Nehemiah, but some claim they are actually 1 and 2 Esdras, which are apocryphal. If the author was making that confusion, or thinking that the author was using “Ezra, two books” to refer BOTH to Ezra/Nehemiah AND 1/2 Esdras, that might get him up to 75 books, closer to the 78 he is searching for. But that would require him to make a series of mistakes, including the fact that Ezra is clearly a different book name than Esdras.