{| Doubts and Discussions about Mahabharata - 2 |} - Page 8

Ganesa having signified his assent, by repeating the word Om! proceeded to write; and Vyasa began; and by way of diversion, he knit the knots of composition exceeding close;by doing which, he dictated this work according to his engagement. I am (continued Sauti) acquainted with eight thousand and eight hundred verses, and so is Suka, and perhaps Sanjaya. From the mysteriousness of their meaning, O Muni, no one is able, to this day, to penetrate those closely knit difficult slokas. Even the omniscient Ganesa took a moment to consider; while Vyasa, however, continued to compose other verses in great abundance.

So, the 8800 verses spoken of, IMO, are those closely knit verses, and not the total number of verses in Mahabharata.

It is also said:

Vyasa executed the compilation of the Bharata, exclusive of the episodes originally in twenty-four thousand verses; and so much only is called by the learned as the Bharata. Afterwards, he composed an epitome in one hundred and fifty verses, consisting of the introduction with the chapter of contents. This he first taught to his son Suka; and afterwards he gave it to others of his disciples who were possessed of the same qualifications. After that he executed another compilation, consisting of six hundred thousand verses. Of those, thirty hundred thousand are known in the world of the Devas; fifteen hundred thousand in the world of the Pitris: fourteen hundred thousand among the Gandharvas, and one hundred thousand in the regions of mankind. Narada recited them to the Devas, Devala to the Pitris, and Suka published them to the Gandharvas, Yakshas, and Rakshasas: and in this world they were recited by Vaisampayana, one of the disciples of Vyasa, a man of just principles and the first among all those acquainted with the Vedas. Know that I, Sauti, have also repeated one hundred thousand verses.

So the established number of verses is One Lakh.

And about the contents, then Chapter 2 of Adi Parva gives a complete summary of the contents.