When you work part-time (i.e. between 1 and 36 hours in a week), you generally use 1 of your 30 weeks of supplementary unemployment benefit.
You can have up to 145.6 hours per month, corresponding to an average of 33.6 hours per week, and still receive supplementary unemployment benefit.
From Factofly's side, we use the start and end date you specify in your assignment together with the total number of hours in your employment contract. You submit this as documentation to your A-kasse.