10 second count, when does it start?

[mjbofficial]

I apologize if this is a dumb question.

I have always started my 10 second count once the ball is touched by the inbounding team on a throw in. A veteran partner told me that a 10 second count actually includes the 5 seconds that are allotted for the throw in. So, for example, if a team takes 3 seconds to inbound the ball, they then only have 7 seconds to get it to their frontcourt.

I can't find any reference in the rule book stating that this is the case and obviously this would have a huge impact on games so I need to know the correct way.