You have a center core of 2 knit stitches running all the way up the sleeve, but each stitch that is added on either side of that core (tree trunk) must remain in the pattern with the established pattern.
This means that you’ll begin every round with k1, then make sure you continue with the established pattern to the last stitch, and no matter what, knit the last stitch.
As the sleeve grows you can see sometimes you will have 6 knits in a row, sometimes you will be in perfect pattern.
You may (as with the Anna pattern) have only one core knit running up the sleeve with increases on either side
The reason for this core running up the sleeve is to mimic a seam, thus keeping the sleeve increase neat-looking and on the underside of the sleeve.
This sleeve increase technique can help you with Cocoknits patterns: Rosa, Mishke, & Anna!