Why couldn't it close at 5:30pm?!!!

I just got delivery notice of a package from 愛知庁内 (Aichi Chounai). That's the big post office in Nagoya City. I have a tingly feeling is about my JET Placement, but the post office is closed, so I can't pick up the package. I WANNA KNOW DAMMIT!!!

*pins and needles* Hopefully I can get it at 8:30am tomorrow, even though the notice says it'll only be available after 4:30pm tomorrow. Dear God, I wanna know what it is!