Why phpfpm_total_processes is a dynamically changing value

[flylan]

I often configure PHP fpm in static mode

pm.max_children=80
pm.start_servers=40
pm.min_spare_servers=20
pm.max_spare_servers=40
pm.max_requests=2000

When the number of active processes does not reach the maximum value, the total number of processes is normal, always at 80. However, once the number of active processes reaches the maximum value, the total number of processes will become a dynamic value, which will be consistent with the number of active processes

Why is the total process not always equal to the value of pm.max_children but a dynamic value?