I've signed off students for solo at 13 hours all the way up to 65 hours. I myself soloed at 13.5 hours. Don't worry about it too much.

A lot of students I've flown with have some magical number stuck in their heads for soloing time. Either they want to be the one out of thier batch to solo first, or solo in the lowest time, or whatever. They tend to focus on that, instead of actually flying the plane and in reality, it hinders their progress.