I'm not familiar with that pattern. But are you confident beynd any doubt that you did indeed cast on 121? If you did, and now you only have 120 then you must have dropped a stitch somewhere, or knit 2 together by mistake.
Is it knit each row for the first 13 - so it's garter stitch? that may be harder to tell then if it were stockinette stitch, but look carefully to make sure you haven't dropped a stitch.
IN any case, I'd likely just increase a stitch somewhere, either at the end of the row or maybe in the middle of the row.
Mirl56 at Ravelry, too.
Learn from the mistakes of others. You canít live long enough to make them all yourself. Eleanor Roosevelt
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