again with the asking for help

Knitters, I need you again.

I got the instruction book for the Great American Aran Afghan a couple of weeks before Daughter's birth. Then I kind of forgot about it. But I just recently dug it out and have started a square. It's kind of a fun thing to work on as an interlude between larger projects. Except I guess I'm totally dumb because I don't understand the charts for the square I'm making. If you don't know anything about this afghan pattern, click away now. If you do have the instructions and/or if you've knitted this thing, please help me out!

I'm working on the second block, designed by Julie Levy. There are 2 charts for this square. You work Chart A, then Chart B, then Chart A again for each row. But chart A has 30 rows, and Chart B has only 28. So what do I do on row 30 when I get to the middle section (Chart B)?

The instructions say to work rows 1-30 of Chart A twice, then rows 1-15 again. So that is a total of 75 rows, right? I tried to do the math to make Chart B line up with that, but 28 doesn't go into 75. I'm confused. Do I just start Chart B over again and knit row 1 of Chart B while while knitting row 30 of Chart A?

The other squares in the book that have multiple charts all have row counts that divide into each other (ie, Chart A has 8 rows and Chart B has 24, so you do Chart A three times over the course of knitting Chart B).

I feel like this must be simple enough to figure out, but my brain isn't getting it. Am I dumb? How do I knit this thing? I've knitted 29 rows and now I'm just sitting here staring at the pattern. Dur. Help!

(Oh, and thanks for all the kind comments about Adamas! I'm waiting for the rain to stop so I can get outside and take some nice natural light photos of it.)