I can set the amount of one coffee/tip. So far I have not changed it from default- 5 eur. But I may change it in the future.

Edit: Now I thought that maybe I misunderstood the question. In that page payments are made with normal money and not crypto. in Ko-fi page payments are made by using either Paypal or something called Stripe. So assuming that someone would want to give me a coffee/tip they would pay from their bank account/card with one of those options.