Guessing Gauge

I knitted a swatch for the Cromarty Sweater from Alice Starmore's Celtic Collection book. According to my swatch, to get the measurements I need for the sweater, I still cast on the same number of stitches. I just think that's weird. Maybe my math is off...with the gauge she gives, it comes out to 6.25 sts per inch. My gauge is 6 sts per inch. She says to cast on 184 sts. That means it should be 29.44 inches across the bottom. The diagram shows 22.5 inches. Where did the other 6.94 inches go? Am I insane? Are they eaten up by seams or the pattern? I need the extra inches. I guess I can knit a couple of rows and see how it measures. I just hate to do all that work just to rip it out and start all over again, when I'm sure someone else has done it already. Duplicating work just isn't my thing.