My question is , how come certain small counties in Georgia has more electorial votes than bigger counties like fulton county. Is each county numbers vary because of the wealth of that county, not the population.

GA gets 15 total votes, the way they are picked is by the political party of the state.

Perhaps you're speaking of the Democrat's primary process? There was a Democrat primary redistricting effort that has gone on over the past few years. From my understanding, I heard this once explained on a news outlet, what happens is shifts in population growths do occur and by the time elections come around the numbers are not proportionate. Like you though, I suspect a certain amount of favoritism could play a part depending on the state's government historic importance in a county, despite the actual population. For example, in some States I could see where the capital seat may be less in population, but receives more count over other larger cities predetermined. Personally I'd count one vote, as one vote, all the same, and do away with parts of the system. But I've heard legitimate arguments on both sides of the issue.