What's 'Reverse Double Mock Rib'?

Went thru a pattern for cardigan and don’t seem to understand some of the instructions

here’s the ones i don’t understand:
[COLOR=“Red”]1) For Back of the Cardigan: Reverse Double Mock Rib: (Multiple of 4 + 2)[/COLOR]
[COLOR=“Red”]2) For Armhole: Mark beg and end of the last row for beg of armhole[/COLOR]

may i know what does it mean?

There should be directions in the pattern for the reverse mock rib–either right after they give you the repeat count (4 + 2) or later on in the pattern.

Tie a piece of yarn or use safety pins to mark the ends of that row. It’s just so you know where to sew in the sleeves later on.

For the armhole, you place markers (yarn tied through a st) in the first and last sts of that row and later that will be used as a guide for stitching up the seams.

Is this the Circular shrug pattern, by chance?