Raglan - I have a hard time seeing how this might turn out

I am knitting the Autumn Pathways Cardigan. It is knit upwards. Four rows after attaching the sleeves I have to start decreasing as follows:
“Decrease 2 stitches in each transition between body and sleeves as follows: work until there is 1 stitch before the marker-stitch, slip 2 stitches as is to knit together, knit 1, pass the two slipped stitches over the knitted stitch (= 2 stitches decreased).”

My question: do I just put the marker back after passing the two slipped stitches over the knitted stitch?

Until now, I have only knitted raglan with 8 markers and single decreases left and right of each line down. I already knitted a special test swatch to get a hang of how this decrease works with my cardigan. I am afraid it won’t render a finished product with an even distribution of stitches on each side in front. It seems that the decreases ‘eat their way’ through the fabric sideways.

How do I solve this riddle? Alas, I used black yarn for my decrease-test-swatch. I will repeat it tomorrow with lighter yarn but I am still wondering how to get the raglan lines go down evenly!