what the heck does this mean?

[KatyKoolkat]

Hey all:
I am attempting the raglan sweater pattern onthis site, but can someone please please explain to me howthe heck you get 'ridges' on a garter stitch? It says to work even in garter stitch until there are 2 purl ridges, then knit the next row, and then do a buttonhole. Hey, here's an idea!! Can someone (or someones) look at the pattern and tell me what they mean and how I am supposed to get a full back of a sweater (ok, it's preemie sized, but come on! they are not fashion dolls!!lol) ?!?

Thanks again for all your help
Katy