You've got two pages out of order. The page when Tim is on his skateboard should follow the page when he's working on the bat-computer in his everyday clothes. You can tell by how the last word balloon on the computer page ("...be home for dinner.") segues to the first caption on the skateboard page ("I'll let you know if I'm going to be later...").
But you're not to blame. DC printed those two pages of Detective #648 out of order. I've seen scans of the original art sheets, and they were marked correctly. But somewhere along the way they got switched.