You are correct. If you want to use two threads you might need to buy more floss. People use both one or two strands of floss on 18 count depending on what look they like.

I have always used two strands on 18 count but the designer must be going for a different look. Keep us posted how it works out. Pam

Hello Mary, from Mary!

Just a couple of weeks ago I began a project that uses Gentle Art Sampler Threads. It's nice floss to work with, it's similar to DMC in that it's 6 strands and has a nice smooth feel to it. It's different from DMC in that it's already cut into 24" lengths, and also in that the skeins contain less floss than a skein of DMC. Just as a guess, I would say that maybe 3 skeins of Gentle Arts floss may be equivalent to 2 skeins of DMC. It's not an issue, I was just surprised to see that my pattern called for 8 skeins of the floss and I thought that seemed to be a lot, but when I saw the floss I realized that it's a smaller quantity per skein

Do you mind if I ask, where in Ohio are you? I've lived in the Washington D.C. area for 35+ years but my family roots are in Middletown, the Cincinnati/Dayton area.

Is this a kit?
If not, I would suggest you do a ‘test’ stitch meaning do 5 full cross stitches with just ONE strand of the Gentle Art Sampler Floss on the edge of your 18-count Aida, then below the row Stitch 5 full cross stitches with TWO Strands of the GAS (Gentle Art Sampler)floss. Now look and see what COVERAGE YOU LIKE BETTER, the one strand or 2 strand.
Also, Gentle Art Sampler Floss is a variegated Floss - you’ll notice the floss color goes to a lighter shade, then to a darker one. With variegated floss, they suggest that you stitch in the ‘English’ method which is to make each X completely then stitch the next X completely and so on; my understanding is by doing each stitch completely you will distribute the color shading of each strand of the variegated floss.
I agree with Mary C. , I enjoy the variegated Sampler Floss, it’s pricier per skein to purchase but I like what it makes the stitching project look like using the variegated.

Thanks to everyone who replied to my question. To Mary C, I live in Washington Court House. Most people have never heard of it and think it's odd. The pattern isn't a kit but I wondered about the floss. There are 24 colors and calls for one skein each. I don't have the thread yet (have ordered) so didn't know about thickness of floss. Can't wait to start it. ☺

Let us know how you like the variegated floss and what the name of the pattern you are stitching. :)