3 in 307 stands for Class A car, which means family car. 07 is a seventh generation car.
The number 4 in 407 stands for B-class car, which means intermediate car. 07 is also a seventh-generation car.
607,6 stands for Class C car, which means luxury car. The French president only got 607.
907.9 is a G-class car. This is a super sports car.