OK before reading this please be aware after typing the below I added this to inform you of my MEGA geekness and the below ended up going from a simple I think this to a full blown maths lesson so my apologies in advance

Well I don't think there's ever been any official the 9th cheveron does this explanation before but I feel it would be logical to assume it's kinda like the 8th cheveron and adds another distance equation.

Because with the standard 7 we have 39 symbols which 1 is unique to each gate the other 38 make the address so if we say the possible addresses available in our galaxy = roughly 3 billion (38x38x38x38x38x38=3,010,936,384) but as is know the symbols corispond to co-ordinates thus only a fraction of these will be valid addresses.

Then the 8th Cheveron is for Galaxy change, but there has got to be more than just 38 Galaxy's out there so the 9th is to take you out of your group of 38 Galaxys I would guess.

I know that Dr. Felger's lab assistant, Chloe, deduces a potential of 63 billion Stargates in the universe, so if were are saying that all nine cheverons could be used that would mean that per galaxy roughly (Asuming there using 1,000,000,000 to be a billion) that there are approx 43,628,809 gates in our galaxy alone if there are an evenish number per galaxy, so that means that only a 1.449% chance of hitting a gate address, which I recon they should have had that licked ages ago

There insane drivel over

ATB
TK Lee

P.S. Feel free to call me a freek

P.P.S. I have noticed in some of my calculation I may have forgotten to compensate for non-reuseal of used symbol, i.e. if you have used the scorpio glyph in the addy you can't use it again, but considering it's late and well it was nice drivel above I shall leave it for now, look forward to a full mathamatical recalculation at a later date, i have bed to goto now