Customer gets resource usage limits notification. However the limits are not reached, yet:
The 'domain.tld' subscription, owned by user 'Plesk user', is approaching or already exceeded the resource usage limits:
Traffic: 100 GB/Month limit / 1071 MB/Month (1%) used / 101329 MB/Month (99%) remaining
Why is 1% usage triggering the "resource usage limits" warning?
Notify when traffic usage reaches set to triggering value in subscription resources usage limits.
Available only if overuse is not allowed. This sets the soft quota for disk space or traffic usage in order to prevent subscriptions from suspension. When the quota is reached, Plesk sends notifications to users' email addresses specified in Settings > Notifications: Resource usage limits
Soft quota can be changed either:
Home > Subscriptions > domain.tld > Customize > Resources
Home > Service Plans >
Service Plan Name> Resources