Decrease now or later?

I’m working on a top down cardigan and am at the point in the sleeve where I need to start decreasing.
The pattern reads …work sleeve even in st st for 1". Con in st st, dec 1 st on each end of needle every 4th row until sleeve measures…
My question is do I start decreasing the next row after I reach 1" or do another 3 rows, then decrease on the 4th row?
Thanks

Do another 3 rows and dec on the 4th.
It probably wouldn’t be fatal if you decreased on the next row but if the pattern really wanted that it would say: decrease on the next row and every following 4th row (or at least it might could say that).