Here only carbon 12th and 13th is not taking part in the resonance. All other carbons are taking part in resonance and lone pair of O is also taking part in the resonance.

As because of resonance stability of compound increases Br will not attack to any carbon which is taking part in the resonance and decrease the stability of compound.

So, Br can only attack 12th carbon or 13th carbon atom but 12th carbon is a alpha carbon and it can easily donate H⁺ ion and add Br^- ion and increase stability.