It just means that for this particular pattern, you have to have an even number of stitches on the needle.
Stitch patterns have 'multiples,' which is basically what you need to follow to make a pattern come out even. Sometimes it will be a single number, sometimes it will be a multiple of 4 +1, which means you need to make sure that your cast on is 9, or 13, or 17, etc.
TMI, I know, but it will come in handy later.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry