[Okay, so since she said that then he didn't think she was in University since that's what he was assuming. (Or he could just... directly ask her but he's dumb.)

Wait. She wasn't a junior high school student, was she?!] Don't tell me you are a middle school student.

You think so? Glad to know that running this shop hasn't made me age or anything!

[... Mikoto you are only 20 soon to turn 21 and you've been only running this shop for 6 months.]