"Turn, drop first stitch, knit back and forth:
WS: p5, k1
RS: ktbl, k3, ktbl, p1 repeat until 5 last stitches, ktbl, k3, ktbl.
5 times each."
Whoops sorry, you're right - these rows repeat for 5 times each. But you drop the stich only on the first row. Then you begin to knit in the round again. You'll be dropping the stitch once there because after you begin knitting in the round again and drop the other stitches at the end, this section below the thumb won't be a part of those stitches.