Did you see these guys and girls shoot. WOW
It is scored electronically but the decimal places only come in during the finals.
During the main competition you are correct in saying that if the pellet obliterates the 10pip or touches the 9 ring etc then it is scored as such.
The Chinese chap who won today scored a 599 and and a new olympic record.
In the finals the closer you get to a perfect 10 the higher your score. A 10.9 is the highest.