They want you to increase within the border to accommodate whatever stitch pattern is within it. So on that last row, just either m1 every few stitches or kfb every few stitches--either will work since it's up against the garter edge.
On the last row, k2tog will work, too.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry