Will my current registrants be overwritten by zoom if I import via csv multiple times

We have currently made prior registrations via mailchimp before we were able to upgrade our account to add a Webinar.

Now we have a webinar link, we have imported the .csv file from mailchimp to the zoom registration with ease. We have also informed new registrants that they can now register in the registration link that zoom generated.

But after all of this, the registration link in mailchimp is still getting some "new" registrations and we were able to generate another csv file of up to  fifty (50) new registrants in mailchimp. 

A little hesitant to import this "new" .csv file from mailchimp as we dont know the behavior of the "import via csv function," thinking that it might override the current list that we have that is now around 400 people.

If we do another upload via csv for the 50 new registrants (from mailchimp), will zoom now add our registrants to 450 people already or will it renew the registration to only 50 registered attendees?

Our webinar is a little less than 3wks from now.

Thank you!

Z