The share of revenue
You do not earn a fixed interest like at the bank. You receive a percentage of what the business actually takes in each quarter: this is what we call royalties, a share of revenue.
If the business takes in CHF 20'000 over a quarter and the contract provides for 4%, all investors share CHF 800, each in proportion to their stake.
What this means for you
The more you invest, the more you receive. With a stake twice as large, you receive twice as much at each payment. It is proportional to your stake.