Feather and Fan Help

I have never made this pattern before but know the sts. I want to put 5 sts on each side for border. I have never made a swatch since all my past afghans already stated how many to cast on.

I am using Premier Ever Soft yarn, US needle 8, 18 sts 18 rows = 4". Each skein is 3 oz and I have 20 skeins. I would like to have 40-45" w afghan. If I need more yarn, I will get it.

The pattern itself is a multiple of 18 sts + whatever side border; I chose 5 sts ea side. It also states the gauge should usually be 5 sts to the inch or more

Pattern Row:

k5, k2tog 3 times, (k1,yo) 6 times, k2tog 3 times rep from * to * until last sts, k5.

Someone else was trying to help me with a swatch but it is not making any sense. She told me to cast on 40 sts and work pattern for 5". For the pattern row I am not able to decipher where she is getting the 40 sts from. I see the 18 sts in the pattern row.

Can someone please help me with a swatch or even how many to cast on using what the yarn calls for? I am so grateful for any help.

Hi and welcome to KH!
The pattern repeat is indeed 18sts so for a swatch, you could do 2 pattern repeats (36sts) plus 5 border sts on each side (46sts total).
For the swatch, you don’t really need so much border but it won’t hurt. You should measure the gauge on the feather and fan sts across the center 4 inches or so.
This is such a lovely pattern stitch. It’ll make a gorgeous afghan.

OMG! Thank you so much.

Thank you for the welcome too.