The pattern is actually telling you that once you’ve completed the cast on of 3sts every alternate row and the increase of one stitch 5 times you’re at 69sts. Then there are 2 more increases on 6th rows to bring you to 71sts. So after the cast ons of 3sts you’re at 64sts plus the 5 increases + 2 increases takes you to 71sts. The pattern is telling you where to place the increases so that you don’t have to choose.
I make a chart with column headings for increases, decreases, cast ons and cast off. The list row numbers in each column just to keep things simple and maintain sanity. You can do this on paper or in a spreadsheet if that’s easier.
Once you get to 71sts we can help with the following decreases and cast offs. It’s a vintage pattern and is heavily dependent on row numbers and therefore row gauge. You should measure the sleeve width as you knit to make sure you’re on track and like the width. It’s a slightly unusual construction with the sleeves knit sideways.
Please edit your post and remove the entire pattern photo. If you could post just the sleeve directions that would be ok. We can’t post large portions of patterns on the forum due to designer copyright.