I just don’t understand these instructions:
Starting Part:
Cast on 41 sts, knit 3 rows in garter st.
At the end of the third row, do not turn and pick up 3 sts on the short side of the rectangle you just knit.
Turn
Row 4 : K3, PM, knit until the end of the row, do not turn, pick up 3 sts on the other short side (47 sts).
Can someone explain it to me? Thank you in advance.
The number of stitches cast on in this video is much fewer than you have but the concept is the same.
THANK YOU! 
You’re welcome. Garter tab starts are a mystery of epic proportion when first encountered. I know how to do it and still marvel at the result. It’s magic. Glad I could help.
You picked a beautiful pattern. I should look at it and see if I want to make it.