score:8
Being 16 years old does not preclude you from traveling to the USA on business, there are plenty of teenage entrepreneurs in this day & age.
Most people refer to a US visa as a "B1/B2" and the majority of visas issued are B1/B2. So your "mistake" of requesting a B1/B2 instead of just a B2 will not be held against you. The consular officials reviewing your application and interviewing you are more concerned with your financial well being and desire to return to your home country. They may choose to amend your application data in their system to be just for a B2 or they may just ignore that aspect.
I would not lose any sleep worrying over it.