Newbie - Help with pattern please - dum question sorry

Hi everyone

I used to knit alot and have recently taken the hobby back up, I’m resuming an old project and have knitted the back of a jumper already however I have a total mind block.

My pattern says:

Starting with a K row, work in stocking st, shaping side seam by dec 1 st at beg of 3rd and every foll 4th rows to 100 sts then on every foll 3rd row until 90 sts rem

So would this mean

Row 1 K
Row 2 P
Row 3 K -1 (103)
Row 4 P -1 (102)
Row 5 K
Row 6 P
Row 7 K -1 (101)
Row 8 P -1 (100)
Row 9 K
Row 10 P
Row 11 K -1 (99)
Row 12 P
Row 13 K
Row 14 P -1 (98)
Row 15 K
Row 16 P
Row 17 K -1 (97)
Row 18 P
Row 19 K
Row 20 P -1 (96)
Row 21 K
Row 22 P
Row 23 K -1 (95)
Row 24 P
Row 25 K
Row 26 P -1 (94)
Row 27 K
Row 28 P
Row 29 K -1 (93)
Row 30 P
Row 31 K
Row 32 P -1 (92)
Row 33 K
Row 34 P
Row 35 K -1 (91)
Row 36 P
Row 37 K
Row 38 P -1 (90)

I really appreciate any help…

Thanks
Anne (UK)

You decrease on row 3 and then every 4th row after that, so in other words decrease on row 3, 7, 11, 15, etc. however many it takes to get you to 100 stitches. Then after that, decrease every 3rd row until you get to 90 stitches. Does that help?

thank you so much, i think that’s got my head straight again!!! :??