Is that kpkpk... next row purl the knits, k the ps?, repeat those 2 rows? What kind of seed stitch? If the kind I described, just count the bumps on a diagonal. Like a 1x1 checkerboard pattern, where you could count the lines by counting the black squares on a diagonal.
If another seed stitch, work out how many rows per square of the checker board, and count the squares in the same way.