ore production

I know there was a thread about this some place, but I can't find it for the life of me ;(

Here is my question. The planet guide tells you the general background about planets. For instance let's take a fire planet, the guide says that it produces min:1,750 and max: 2,500. However out of 5 fire planets that I took over, the ore collection ranged from 600-to-1000.
Does this mean that the guide is wrong? That it's a bug? Or that there is some unknown factors (skills or orbitals) that when combined will actually produce the stated value in the guide?

Could someone please shed some light on this?

Yeah, I'd also like a good explanation on this as well. I have to assume (and you know what they same about that) that the potential production is what they state and the actual production is limited by tech/population. As I know when I'm scouting planets to mine or colonize that the stated production of the planet pre-outpost/colony is always higher than it is once I take it over.