First time knitting a sweater and I need help please

This is my first time posting here. I am just starting out on my first big project and have nobody to help me when I get stuck. The only other item I have knitted was a scarf and that was straight forward and I didn’t use a pattern. I just did a knit two and purl two to get a rib stitch.
Now I am branching out and attempting to knit my first sweater but already I have encountered problems and was hoping so much that somebody here could help me out. I have just finished a garter stitch band and then 10 rows of stockinette stitch and it looks nice.
I am knitting a size medium.
I understand this following row;

Dec Row (RS): K1, ssk, k across to last 3 sts, k2tog, k1.

But I am baffled by the next row;

Rep Dec Row every 10th row, twice more *54 (61,68,74)sts. Work 9 rows even.

I do understand that it means Repeat Decrease Row but that is it.
Is there any one who could explain to me in detail what it means. I would be so very grateful as I am eager to continue.
Thanks :wall:

You do the Dec row the first time, call that Row 0. Then you work 9 rows in stockinette st, and on row 10 dec again, then repeat it. Work even means to knit the rows without decreasing.

Thanks very much for explaining that Sue. I follow everything that you wrote but I’m sorry but I still don’t understand the part where it says - twice more *54 (61,68,74)sts?

After the 3 decrease rows, you’ll end up with 54, 61, 68, or 74 sts depending on what size you’re making.

Thanks Sue, I think I understand.