srivathssa I believe this is referring to the specific key itself. This is usually the case if you are not specifying a URL that this API key can be used for - meaning that if somebody were to get ahold of this key, they could use it for any website (thus charging this google account for usage). So its best to specify the domains that this key will be used on. You can list as many domains as you'd like - including the webflow staging url (your-website.webflow.io) etc. So that this recaptcha works on production and staging, etc.
I'm kind of taking a shot in the dark based on some past experiences so I'm like 85% sure that this is what this means.