You misunderstand, you take as many as you need (there’s a limit in theory but that’s… Complicated), it’s just that after 3 days you are paid by the welfare agency, not your employer. For you it’s the same, you still get your usual paycheck and your employer wires you the money, but they are reimbursed.

It’s an answer to the frequent criticism “but if you stay in sick leave for a long time it’s damaging to your employer!”