It says "each first annual install per year over a 1 million threshold" which I think means as long as you're updating your app at least once a year, you pay for each device your app is installed on (minus 1 million, which is a rounding error for the biggest apps).
shagie|2 years ago
https://developer.apple.com/support/dma-and-apps-in-the-eu#d...
> First annual install. The first time an app is installed by an account in the EU in a 12-month period. After each first annual install, the app may be installed any number of times by the same account for the next 12 months with no additional charge.
Multiple devices with one account or new devices over the course of the 12 months are still a single install.