Expiration date on box

The box says it expires in August 2014, and each individually wrapped test stick says has a stamped ( I assume expiration) date of July 2014. Does that mean each stick must be used in July before it expires in August? Or was there an error on the box, and it should have matched the individually wrapped test sticks which have the date July printed on them? And do these REALLY stop working by the expiration date? Or are they just a percentage less effective? Would be a shame to have to throw these out in less than a month. Thanks!