How to change size of title's text on Action Bar?

Question

There is an ActionBar on each Android 4.0 application, and it got a title. I need to make this size less. But I don\'t understand how I can do it, because

Answer 1

on my system, res/styles AppTheme has a note saying

and this is the style indicated in AndroidMainfest.xml. I added

15sp

and it worked and I'd rather do this than a custom actionbar.