Pattern help sleeves in the round

I’m knitting the Akoya cardigan by Carol Feller. Done in the round bottom up. Now stuck on sleeves. Don’t understand pattern - underarm set up round. Have 74st on circular needle. K8 sts , place previous 16sts on waste yarn (half from start of end and half from end of rnd). Should have 58st on needle.
Am at the start of rnd so do I k8 then put these on waste yarn with 16sts. Don’t understand how I could then have half from start of round and half from end of round. Also the k8 would have an extra row. Please help if you can

Welcome!

Start the round by knitting 8sts. Place these 8 after the beginning of round marker on waste yarn and then place the 8sts before the beginning of round marker on the same waste yarn. You’ll have 16 underarm sts on the waste yarn, 8 on either side of the marker.
It won’t matter that they are from different rounds. One row will only make a small fraction of difference.