Now it goes round
There is an error in the chart for the basic construction. It has one more increase than decrease rows. To fix it either:
1) Start with 9 stitches, not 11 as shown in chart, and do an additional 2 rows, one decrease row and one purl row. This is what the knitter has done in the striped sample; or
2) Do not increase on row 19, but work straight.