garter ridges....

[EmilyKaye]

I'm attempting to knit a blanket from the Mason-Dixon knitting book. It's a log cabin design, but I have a question about some of the directions. I know it's something that I SHOULD know, but I'm rather slow when it comes to simple things! It says to cast on 20 stitches, then knit 24 garter ridges.
Does that mean I count garter ridges only on one side of the work or on both sides? Believe me: I go through this with every pattern. My mom says I try to make everything harder than it should be, but she can't help me because she doesn't knit. I'm rather embarassed but my lack of simple knowledge, but I can't be the only one out there!!!