Cute pattern. Is this where you are?
CO 52 st and join in the round. place marker. Knit in stockinette st for about 15 cm/6"
Decrease 2 st. evenly on the next row
Knit 5 rounds of the garter stitch pattern
Are you doing magic loop? I have a tendency to get a yo at the point where I pull the needles to start knitting on the other one. If I were going to just continue and do an extra dec I'd do 3 - k2tog or p2tog whichever it would be.
I should never overestimate my basic arithmetic skills.