Explanation
Box 1: Number per user over a sliding window of time
Service protection API limits are enforced based on three facets:
The number of requests sent by a user.
The combined execution time required to process requests sent by a user.
The number of concurrent requests sent by a user.
The following table describes the default service protection API limits enforced per web server:

Box 2: Combined time per user over a sliding window of time
Box 3: Fixed number per user
Reference:
https://docs.microsoft.com/en-us/powerapps/developer/data-platform/api-limits