on the dot

"dot"とは、”点”のことですが、その点にぴったり合うということで、"on the dot"は、


（時間が）きっかり


という意味があります。時計の文字盤で、分針がある1点にぴったりと合うイメージです。


At 8:14 a.m. on the dot, the store's neon "open" sign was switched on. The crowd clapped and cheered. Bagpipes played. Chief Farrar, coffee cup in hand, emerged from the store along with Forza Coffee Company Chief Executive Officer Brad Carpenter. They greeted every person in the line, which by then stretched more than a block from the store's front door.
(Cafe where Lakewood officers were shot reopens. The Seattle Times. December 12, 2009.)


即金で（直ちに支払う）


という意味もあるようですが、実例が見当たりません。