Explanation

Box 1: 3
At 6:00 the default 4 instances are running. The CPU utilization averages 10% for 25 minutes. The scale in rules states that 1 instance should be removed when CPU utilization averages 30% or less over a 20 minute period.
Box 2: 6
At 6:00 the default 4 instances are running. The CPU utilization averages 70% for 25 minutes. The scale out rules states that 3 instances should be added when CPU utilization averages 70% or more over a 20 minute period. However, the maximum number of instances is set at 6.
References:
https://docs.microsoft.com/en-us/azure/architecture/best-practices/auto-scaling
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-understanding-settings