Work one row even just means to work the row as you have been, without any increases or decreases.
Work 17 stitches as you have been working them, do the decrease, and then finish the row in the established pattern. It looks like these two rows are even rows, so it's basically to purl except for the edges.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-c