Should sk2p decrease by 1 or by 2?

I’m working on a pattern with a sk2p (slip, knit 2 together, pass slip stitch over). Am I correct to assume that this will decrease the number of stitches by 1?

(slip, knit 2 together, pass slip stitch over) this will decrease by 2. It’s taking 3 stitches and making it one. you slip one stitch, than knit 2 together (decrease #1) and then pass the slipped stitch over and off the needle (decrease #2).

Thank you for your help. I was doing it wrong, I was passing the slipped stitch over to my original needle instead of passing it off the needle.