Cable schematic help

So I’ve found this pattern and being rather new to knitting just wanted to check that I have this straight in my head.

I’m doing this in size medium.
I understand that I need to do the cable patterns from the schematics. Thinking of starting on row three? Hopefully that’s a logial place to start.
What I’m slightly confused with is the start it says establish pattern (rs) work in rev st st then in the size M instructions, it says keep in st st I’m thinking looking at the schematic that it should be st st. )?

Very nice looking sweater. I just love Aran knits.

The background for the stockinette cables on the RS is reverse stockinette stitch. For Row 1 (RS) the directions fill in the spaces between cable charts with purl sts which should be knit sts on the WS (reverse st st).

The edge stitch is however, kept in st st throughout.

I’d start with row 1 of the charts unless you have another reason to go to row 3?