They don’t ask them what they want to pay or what they claim the revenue was, they look at the numbers:
Art. 83(5) GDPR, the fine framework can be up to 20 million euros, or in the case of an undertaking, up to 4 % of their total global turnover of the preceding fiscal year, whichever is higher.
EU law: “How about percentage of global revenue per infraction?”
Meta: “Okay. 0.00001%”.
They don’t ask them what they want to pay or what they claim the revenue was, they look at the numbers:
https://gdpr-info.eu/issues/fines-penalties/
Although realistically speaking they’re probably just getting fined for one “infringement”, despite committing quite a lot.