You need to use the encounter code first to find if you can catch a mangemite. When you generate method J spreads, right click on one of the frames that is a shiny spread (you should have a few different ones) and it will tell you the encounter slot for that frame. Look it up on the encounter table and you will see what pokemon is on that frame. Do this until you find one that gives you a magnemite. As far as calcs for your journal flips go, you should be doing 978-2-0 roamers = 976. 976/2 = 488 journal flips. Make sure you saved in the grass so you have no need to walk around when sweet scenting after you've completed all of your flips.
Ahh I see, I now face a different problem
I've gotten a "seed" from spreads already generated which you can download from the OP. My seed is C8120291
What do the "frame" and "Actual" frame mean? Which one am I meant to be aiming for? Sorry for the silly questions =[
Also, I right clicked on calculate encounter slots. It said sweet scent in grass/cave is 7? What does this to to my overall flips? O_o. I clicked on diamomn encounter slots webby, it said magnemite is frame 0 or 1. Does that mean it has a chance of appearing on both? (swarm of course). Is this certain they'll appear? Or is it only a % chance it'll appear?