Hi, I've been using Vamo's for over 6 months now ands see this question come up for people.
NO 1 is an average. In real terms - it fires higher than the setting on the display. So, for example, you have a 2.6 ohm attachment (cartomizer or clearo), and set the Vamo for 7 watts. Instead of firing at 7 watts it fires at 9.7 watts - quite a difference. I didn't just make up those numbers - they are test numbers from tests done on Zmax's - which have the same chip as the Vamo. Some vapers like a harder hitting setting and use this - not that many tho.
In NO 2 mode, RMS, what you set on the display is what the Vamo will fire at.
So again, lets say you have a 2.6 ohm attachment and set the Vamo for 7 watts. In no 2 mode it fires at 7 watts. So its more accurate, and you don't get any unpleasant surprises from it firing higher than you wanted.
I can't remember what the setting is when it ships. Its very easy to change it tho. Just hold down one of the small buttons for about ten seconds until you see either NO1 or NO2 on the display. Whichever one you see is the one its on. So if you see NO1 hold one of the small buttons down until you see NO2. Then leave it there.