Crocheting a Schnuffeltest

Hello, I’m stuck on a pattern right now, and it says: 

41 chain stitches1. hdc in 2nd ch from the hook, 1 hdc in each of the next 38 stitches, 2 hdc in the last stitch, continue working on the underside of the chain, 1 hdc in each of the next 37 stitches, increase in the last stitch (80)2.-26. 80 hdc (80)

27. 18 hdc (80)
maybe someone can explain it to me in a way I understand.. I can’t get any further from “continue working on the underside of the foundation chain.” Does that mean I have to crochet in a rectangle, so all the way around?
and why the 18 at the end? 

Good morning, yes, that’s how I’d do it. You crochet the foundation chain from the top; the 39th and 40th half double crochets go into a chain stitch, and then you crochet back down the foundation chain. Double the last stitch. I’ve attached a picture I took—the stitch count doesn’t match, though; it’s just an example.



 Rounds 2–26: Always 80 half double crochets in the round—this closes the bottom of your crochet piece and makes it look like a bag.

  Unfortunately, I can’t explain Row 27 because I don’t know what your project looks like.

Did you purchase the pattern here on CP? If so, why not ask the author directly using the contact form? She’ll be happy to help and can explain it best. 

I suspect there’s a typo in row 27 and it should say 80 hStb instead of 18 hStb. 

So, first of all, thanks for the answers—it’s a little clearer to me now. However, it doesn’t make sense to me if row 27 is also supposed to be 80 hStb; otherwise, they could have just written 2–27 in the pattern...

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This is what it’s supposed to look like when finished...

Good morning, what exactly is this supposed to be? Is it perhaps crocheted together at the top after the 26 rounds?

If so, then instead of 18 half double crochets, it could be 38 half double crochets. So maybe it’s a typo after all

Based on the section of your image, I can see that the pattern is by Lotta Leben. It’s best to contact the author directly; she’ll be the one most able to answer your questions.
Here you can access the contact form

Hello

you can message me anytime if you have questions about one of my patterns. 
I’m also happy to explain it again here. 
you crochet around the foundation chain at the beginning and then continue in spiral rounds. This creates a slight offset between the stitches after each round. To even this out at the end, and so that you end up at a corner of the shawl, you work the 18 hStb. 

Best regards 
Martina from Lotta-Leben

Before crocheting the 18 half double crochets.