What does the Google Play app refund process look like for a developer?

Question

Google Play

Hello.
As far as I know, Google takes some percentage of the amount for a paid application sold on Google Play. In this regard, I would like to know how the refund process for a low-quality application looks like for a developer.
If the user requested a refund (it seems that he can do this most quickly within 15 minutes after the purchase), then what amount is deducted from the developer's account - exactly the one that he received for the application or is there any other commission, fines, etc. .? In the event that a bug is found in the application, for example, and users begin to return money en masse, is there a risk of being in the red / in debt?