I THOUGHT I had the math correct for a bath mat, but no, it's way off. The problem is how many stitches to cast on, leaving off stitches on the ends. Is it possible that a pattern like this won't lend itself to being increased?
So, decided to make like a frog, and rippit, make a dishcloth first. Not a knitted dishcloth fan, but think it's the only way. Tomorrow is another day.