Increase purlwise question

It knitted the basque (ribbed section) of my Men’s Raglan Sweater and the instructions say:

Using 3.25 mm cast on 141, knit 1 x 1 rib for 21 rows. (done)

K1, * inc purlways in next st, K1, rep from * to last st. 221 sts.

That’s an increase of 80 sts over 140.

That seems like an odd number, but I could be just daft.

That’s correct, 80sts over the 141sts that you start with. You’re essentially increasing every other stitch. If you finish the row, count sts and find you’re under or over for whatever reason, you can always adjust the count on the next row.