A field service organization is implementing a new entitlement management system within Microsoft Dynamics 365 for Field Service. They want to ensure that their customers receive the appropriate level of service based on their entitlements. If a customer has a service entitlement that covers 10 service hours per month and they have already used 6 hours in the current month, how many service hours do they have remaining for that month? Additionally, if the organization has a policy that allows customers to roll over unused hours to the next month, how many total hours will the customer have available at the beginning of the next month if they do not use any additional hours this month?