Google Analytics after migrating a domain


I have some confusion regarding the google analytics after publishing our new website on our custom domain.

Before doing our redesign, we hosted our old website elsewhere (always the same domain) with a google ID tracking code.
When we started designing our new website in Webflow, we generated a new google ID tracking code that should be used for the new site. Once we migrated the domain, in the analytics I am noticing that the we have data for both the old and the new website (always same domain, different google ID)

Shouldn’t the analytics for the old website be equal to 0, as no one is actually accessing it?
How can this be fixed and does it mean that some people are actually seeing the old website instead?

Thank you for your help! :slight_smile: