As many as you like. There is no subscriber limit on the Free plan. What Free is limited by is money: up to $500 of subscription revenue per 30 days, measured over a rolling window and converted to USD. Two hundred subscribers paying $2 each is fine; ten paying $60 each is over.
The Pricing page shows the figure the limit actually uses. Do not read it off the Active subscriptions card on the home page, which counts contracts instead.
What happens when you pass it
Nothing that day. The app warns you at 80% of the cap, and once you cross it Pricing shows a grace period with a date: 30 days to decide. After that the only change is that the subscription widget stops appearing on your product pages, so no new customers can sign up.
Everything you already have keeps running: existing subscriptions keep billing, the customer portal still works, the Mollie engine still charges, and no data is touched. Saving a plan is not blocked.
If you need more room
The paid plans raise the cap and change nothing else: Growth $29 covers $10,000 per 30 days, Pro $99 covers $100,000, Business $399 has no cap. Every plan charges 0% commission. "What each plan includes" compares them.
Stuck on any of this? Open the chat in the bottom right corner of the app and we will help you set it up.