what does your pill leaflet say, some vary with instructions. But reguarless to how many you take. You will still need to use alternative protection, if you plan on having sex in the next 7 days.
Edit: im on mircogyon, and my instructions say take the late pill as soon as you realise and the next one at normal time. I would leave a few hours between them though. You have a 12 hour window before its consider late, so the second pill gives you a bit of a gap between them.