Presumably what was paid on top of the minimum price?
Viewing post in Question about TIP
People can pay whatever they want above the price.
If your game is paid, and you charge X or if it is free but has a minimum of X as a donation and someone wants to support you or really liked your product, they could decide to buy it or donate to you for more than the value you ask, for example pay X+T
That difference above the value you set is called a tip