Missing information: Crochet Hook Size 6 mm J

Errata: Page 3 Top right column should read: “Make sure you are using the correct size ball for the color blocks: we start here with Color A in a short diagonal so we need the 56 gr. ball.”

Confusing math and sets of stitches clarification questions:
Question 1 confusing math:
When you join the next color block you create an extra chain every time. This chain counts as chain number 20 for each color block. This is why the end color block needs to be 20 chains. This way all the blocks have 20 chains each. It was my fault for not explaining that little detail which is a very important one.

Question 2 how many sets?
Row 1:
1sc into the third ch (2 sts) this is correct
Ch 1, sk ch, sc in the next ch (2 sts not 3) you are skipping a chain but adding a ch in between stitches.
Repeat this set 7 times. This equals to:

2 stitches x 7 times = 14 sts add these 14 + 4 previous sts = 18 sts + the last sc = 19 sts. Where is the final stitch?

Let me explain:
When you add the next color block this is your stitch #20th . Confusing isn’t it?? It is a confusing math!! I don’t know if it is because of adding the color we tend not to count that stitch.