Shaping Sleeve Conundrum....

[jezka]

I'm having a bit of trouble understanding part of a pattern and hoping some of you could help me

The pattern reads (for a puffed sleeve cardi currently knitting the back of the work bottom to neck)

Shape Armholes
Keeping stripes correct, cast of 3 sts at beg of next 2 rows. 61 sts.
Dec 1 st at each end of next 3 rows, then on foll 2 alt rows. 51 sts.

The part I'm stuck at is underlined. To my mind, if I dec 1 stitch every 2nd row, then one side will be 'lop sided' wouldn't it?

Thanks in advance!

Knitting Newbie