Never mind, I found it in the user_guide.html:
You can also set the maximum number of products that get a percent off. Using the same example, lets say you want to give a 20% discount up to 10 items and then no more discounts. This can be done with the following value: 1-10;2-20;11-0;. The input field is very specific. As a definition this can be broken down to [quantity]-[value];[quantity]-[value];...etc etc.