Subscribed, unsubscribed, and non-subscribed contacts all make up your contact count. The number of contacts you store across all of your audiences in Mailchimp. Your maximum contact count affects the price of your plan. Archived, cleaned, and deleted contacts do not count toward the price of your plan.

Should I delete unsubscribed contacts in Mailchimp?

To conclude on what to do with Unsubscribes…

If you aren't using any of mailchimp's other marketing tools, it's best to Archive them (and even if you're on a legacy account and don't get charged for unsubscribed contacts, it's not a bad idea to archive them as there isn't a penalty for doing so).

What happens to unsubscribed in Mailchimp?

When someone clicks the unsubscribe link in your email campaign, they're automatically removed from the audience that received the campaign. Mailchimp scans for high unsubscribe rates because they can hurt your reputation and deliverability.