It'll be pretty easy to tell which size you have just measure how tall it is.
Here's the quick and dirty on the spec sheet. Where it says Fresnelite 6"spot means when the
Fresnel is in spot or adjusted all the way back. Looking at the graph Ther first bit distance is how far away from what you're shooting, Beam is how big the circle of light will be on the ground, and illum is the measurment in FC or how bright it will be.
The next chart down is the same in flood, or when its adjust all the way forward.
Wait...reading it further I guess the focus is a adjustable arm on the back of the light...there'll be a little graph on it to tell you if you are in spot or flood or somewhere between.
Anyway....if I'm shooting from say 13 feet away with the 6" Fres and I want the light to flood everywhere... the light is going to be about 14' big...this is a little bit of guess work because I'm looking at how big the light would be at 10 feet and at 15 feet and finding the number in the middle