Heart Double Knit Hot Pad

Help! The pattern calls for cast on of 30 dble stitches to equal 60 workable stitches and the chart shows only 29 squares per row. Each square counts as “two stitches”. Do I not count he first slip stitch and the last purl Stitch? I got the pattern right on this web site. I started it and it’s really cute.

Did you watch the video on double knitting? It demonstrates this very pattern.
It would be in the “advanced techniques” section.