Deciphering Raglan instructions

Looking for help to decipher instructions given for a child’s striped jacket in Bergere de France Caline. size for 12 months.
I’ve got to the Yoke section where all the different sections of the jacket are brought together by picking up all the stitches. I think I’ve worked out the pattern of the stitch decrease but I am now stuck at the 12 months size instructions – “On foll 4th row, then on foll RS row” rep from “to” 5 times, then every following 4th row 6 times.
1.Where exactly does 4th row come from? 2. Do I knit a straight row in between each decrease.? 3.When it says “then on every foll 4th row 6 times” what do those 4 rows consist of after having done the previous decrease pattern 5 times? Why and how is it different to the 5 ?
Sorry I hope you’ve been able to work out my confusion, I’m finding it difficult to explain what I don’t get!
Thank you

Lovecrafts is having trouble with their site so I haven’t been able to pull up this pattern yet.
https://www.ravelry.com/patterns/library/inedit-n5-gilet-en-caline-striped-jacket
Maybe that’s the one?

Starting from the last instruction, call the next row, row 1. Then decrease on rows 4 (I’m assuming this is a WS row), 5 (RS), To repeat this 5 times you would decrease on row 9,10, 14,15, 19,20 and 24,25. Then dec on rows 29,33,37,41,45 and 49

The rows between decrease rows are worked without any decreases.

I’ll try to pull up the pattern to make sure of this. You might check stitch numbers if they’re given to make sure there are enough repeats.

Yes you have the right pattern, I need to concentrate on this and let you know how I get on, thank you once again for your help

Just to let you know that your explanation has been fantastic. Once I sat down and read through it , it made perfect sense, why on earth don’t they write things out as clearly as you in the pattern instructions, especially for the inexperienced ! it would save a lot of time and frustration.
Thank you again.