Thanks Sue, but the problem is...
I get 11 stitches left on the 17th time on the RS, as the pattern says to end. What I have to do after this is
1) WS : bo 2 stitches --> 9 sts left
2) RS : continue with both arm and neck decreases
- arm decrease for the 18th time : K3, KSP, k to end = 8 sts left
- neck decrease : 7 sts left
3) WS : purl across, decreasing 1 stitch for neck : 6 sts left
4) RS : continue with both arm and neck decreases
- arm decrease for the 19th time : K3, KSP, k to end = 5 sts left
- neck decrease : 4 sts left
5) WS : purl across, decreasing 1 stitch for neck : 3 sts left
6) RS : continue with both arm and neck decreases
- arm decrease for the 20th time : K3, KSP, k to end = at this point, I'm not sure what to do since there are 3 stitches left and I cannot KSP after the third knitted stitch