Help with casting on as increase

I already posted my question once but I think I was in the wrong section. I’m new to the forum.
Anyway, here’s my predicament:
I’m knitting a tank top and I’m to the point where I start the upper band.
I’m supposed to switch from #7 needles to #6 circular needles.
The directions say: "next row (WS) using #6 needles, CO 30 sts, p across bodice sts, CO 30 sts."
I only know how to use a single cast on to increase and that doesn’t seem to work here. I’m so confused!
I’m so happy to find this site.

What I would do is cast on 30 stitches (single cast-on) and then purl across them and the bodice stitches, then cast on 30 more at the end.

Yes, the one side will have one more row than the other, but it won’t matter in the end.

Yes, I agree.

Alright, that makes sense. I was actually thinking that might work but then second guessed myself because the upper band of the top is worked in garter rib and I thought that not purling those last 30 CO sts would mess up the pattern. Trust the pattern… that will be my mantra as I finish the top.
Thanks again.

Unless I’m doing something REALLY wrong, I don’t think it worked. I casted on 30 sts, purled them and the bodice sts, and then casted on 30 sts at the end of the row. The problem is that the next row I’m supposed to start the upper band of the top in garter rib. The pattern is off. It doesn’t match the lower band. Oh, I’ll just frog the last few rows and try again…