Overage and Regular Billing hours

Hi, I am trying to figure out where Pulseways bases the overage time and regular billing hours in the system.

You see, I created the retainer hours and added 8 hours to a ticket. I expected that the 8 hours would appear in the regular billing hours during the billing review, but it wasn't distributed that way. Instead, 6 hours were counted as overage hours, and 2 hours were included in the regular billing hours. At first, I thought this was due to the working hours, but I guess it is not related to that. Can someone help clarify this?