Is this a typo?

This book seems full of mistakes. Again Easy Baby Knits Matinee Jacket publisheris ryland peters & small. Ive looked all over for corrections and I cant find any. So heres the problem. Im making the sleeves and the instructions read as follows :
cont in seed stitch inc 1 st at each end of next row and every foll 4th row to 37 (43:47) sts.

Then it says 2nd and 3rd sizes only (Im making the 3rd size)
cont in seed st inc 1 st at each end of every foll 6th row to (43:47) sts

So do I do it every 4th row or 6th row to 47 sts? or is the 47 sts a typo in the 2nd part of the directions? TIA

I think you’d do it every 6th row for the larger sizes because that would stretch out the increases to get to 47 sts and would make it longer. Probably the (43:47) shouldn’t have been there in the part for inc on every 4th row.

Thank you sooooooo much.