Sizing in pattern

Can anyone explain this please I’m knitting 4th size. I’m decreasing my stitches in a sleeve and not sure what this next bit means … decrease in 3rd and foll
4th ( 0:0:0:0:0 ) row.

Welcome to the forum!
Whenever there’s a zero or a dash for your size, skip that direction and go directly to the next direction.

do you mean by skiping that direction that we should not knit a row without decreases?

For the direction given in the first post, knit the decrease on row 3 and then go on to the next direction for the 2nd-6th sizes, whatever that direction is. There’s only the single decrease.
For the first size, decrease on rows 3 and 7 and then proceed with the pattern.