Hi and welcome to Knitting Help!
It depends on what the blocks in your chart repeat are telling you to do. There may be yarnovers in the chart which don't use a stitch but do take up a block or k2tog which takes up one block but requires two sts. Can you write out the first line of the chart whcih is causing trouble and tell us which section is repeated? or give us a scan of the first few rows?
Can you post a link to your pattern or chart or give us the pattern name?