The first digit of the extension is the dealership.
10000 = Hansel Ford, Hansel Mazda
20000 = Hansel Campus – BMW, VW, Acura, Subaru
40000 = Hansel Toyota
50000 = Hansel Honda
60000 = Henry Curtis Ford
The second digit is the department
1 = Sales
2 = Service
3 = Parts
4 = Business office / Admin
5 = Shop / Detail
The final 3 digits is the extension
So as an example: if you see 42373 displayed on your phone you know that someone from Hansel Toyota in the service department is calling.