Charlie,
Different agencies use different variations of codes.
10-7 generally means 'out of service' as in 'off duty' or 'off shift.' Some areas may use it differently.
10-10 was what we used for 'out of service, subject to call,' or, available for emergency, in other words, a temporary break. Other agencies may use it differently.
As an example, the three largest agencies in Arizona (Phoenix PD, Arizona Dept Public Safety, Maricopa County Sheriff) use 10-7 to indicate 'out of service.' AZ DPS uses 10-10 as 'out of service but available,' MCSO uses 10-10 to indicate a negative or 'no' response to a query, and Phoenix PD does not use 10-10 at all.
Another large agency, Pima County Sheriff's Department, uses 10-7 the same way, 'out of service,' but uses 10-10 to communicate 'fight.'
Your mileage may vary.
PS: I think in Vegas 10-10 means 'out of chips.'