Ok, so I did more math on this than I ever wanted to do. Basically, this whole thing is a paradox.
So it turns out that the chart IS only supposed to be 69 rounds. I read the instructions incorrectly. It was the stitch count on row 69 that was like 77 stitches or something. Still, in my defense, it doesn't read very clearly. And it doesn't change the fact that the chart, when knitted, looks different than the pictured garment.
Also, the gauge is written as 19 rows for 4 inches. Ok. I am getting that or very close to it, despite using the smaller needle (not my fault). Well 69 rounds equates to about 14.5 inches in length. At what point does the length end up being 20.5 before the fringe? Can't be blocking. It's fair isle. It won't stretch out but only so much. Maybe that's the length with fringe? Not what the pattern shows, though. Brain hurting.
I did make the chart longer by one pattern repeat. This increases it by about 17 rounds. But I think that either A) I will run out of yarn, or B) it will be too long.
So here's what I think I'm going to do: before the bottom charted border, I will add like 5 rounds of a simple, repeating heart pattern. Something like this: