Documents from the lawsuit Lil Wayne filed against Birdman that have been obtained by TMZ reveal just why Wayne is so angry at Baby.

Wayne and his team believe Birdman wasted $70 million of the $100 million Universal Music Group advanced Birdman for a Young Money distribution deal -- money he was supposed to share with Wayne.

Birdman claims he spent the "lost" cash on royalties marketing and recording expenses. But Wayne's not buying it, and wants the court to force Baby to open his books.

While Birdman's camp has handed 22,015 pages of docs over in lawsuit so far, not a single one of them details how the $70 mil was spent.