https://gdpr-info.eu/art-83-gdpr/
"Infringements of the following provisions shall, in accordance with paragraph 2, be subject to administrative fines up to 20 000 000 EUR, or in the case of an undertaking, up to 4 % of the total worldwide annual turnover of the preceding financial year, whichever is higher:"
Proportionate how? That's obviously up to them to decide and they probably mean that large companies like Google will be subject to the 4% instead of 20 million euro. Are you going to bet your life savings that they will fine you 4k euro instead of 1 million euro?
Why would they bother to add the phrase with "whichever is higher" if they were even going to consider a fine lower than 20 million euro? Think about it. They don't care about the fine being proportionate to the downside, they are just worried about it not being strict enough to companies like Facebook and Google.