What happens when the contacts' count in a sync exceeds the contact limit of my current subscription plan?

What happens when the contacts' count in a sync exceeds the contact limit of my current subscription plan?

We will automatically upgrade to the next subscription limit if the contacts' count in a sync exceeds the contact limit. The adjustment in your subscription plan will be reflected in the upcoming billing cycle.

Note: CRMPlus and Zoho One users has to upgrade it manually.