Youtube API call with OAuth2.0 use or not credit/quota?

I have a question about Youtube API V3. And generally about Google APIs.

For example, on my website I use the Youtube API for have a 'Subscriber' button that really add a subscrition on a channel.I need to use OAuth2.0 to insert that data in the account of the user of my website.I know that the OAuth2.0 don't spend "Youtube API credits/quota".But I want to know if the credit for the API call "insert" will be on my quota or not? Maybe that action don't spend credit because that's on user private account?

I need to know that, to estimate my consuption of credits and so know how large my quota need to be.

Thanks for the information and advice.Cordially