Let's say my daily income is 500 sat and the estimated daily income to 1000 sato. This means that 50% of my traffic is unsold and you would is it for affiliate ads? Is that correct? On the other hand, if the daily income is higher there is no 'unsold' traffic? Do I understand it correct?
Sorry, didn't understand what's the difference between "my daily income" and "the estimated daily income", perhaps you just confused the words.
If you mean that the wanted daily income is 1000 and you earned only 500, then, yes, you understood it correctly. That also means that advertisers that pay you will get only 50% of your traffic, the remaining will be used for free affiliate ads.
During the time another question came up where I could find no explanation to. It is about the rewards. How do they work? Do you get them randomly or you have to do something for it? I know that I got like 2 rewards right after using a-ads but after some time there were no rewards anymore and I started to wonder how they actually work.
There are advertisers that reward publishers for visitors that turn into paying clients. If you got a few rewards, then you probably displayed ads of such advertisers (perhaps, free affiliate ads, but not necessarily) and attracted customers to them. Sometimes advertisers add a text comment to the reward so that you understand what you got it for.