He was guaranteed income outside of his contract. This involved the club providing contacts to his manager for media appearances, advertising etc. This is a legitimate source of income.
The problem was that Tippett often couldn't be bothered getting off of his arse and attending or following up on these leads. As a result his manager went back to the club and demanded the shortfall in this promised income. The club paid the extra money which is where the payment breaches were made, although the club in fact didn't exceed the TPP.
There was a really good article in The Age explaining a lot of this a few years back. Might be this 1.
https://www.theage.com.au/sport/afl/the-tippett-saga-how-it-went-wrong-for-crows-20121128-2aefe.html