I was horribly mistaken. I thought Misaka was one of the few level 7's, and Accelerator was trying to get to level 8. I guess i just got the numbers mixed up.

Regardless, there's still some conflicting material here. In Index, Misaka met Touma for the first time on that bridge the night before he met Index. In Railgun, she met him for the first time in that back alley. It would only make sense for that to be their first meeting in the "Railgun universe," since she wouldn't attack him otherwise.