There are two views I would consider valid. One, you are a co-founder getting some split of the equity. Who then turns around and sells your equity to the other founder(s), this is where your salary comes from. Second, You are really employee number one. The founder(s) are giving you a nice title and a sign on bonus of 6% equity.

On the whole you give way too little information on the deal to make a real call. Though it sounds closer to the second option than the first.