not quite sure what you mean.
if the issues are occurring after you "export for web" then i would have to say that it only exports the 1 slice because, you have it set for "export selected slices only" instead of the "all slices" setting (that's found in 'save optimized as' popup)
now if you are having issues with your button being larger than your slice, then i would just resize your slice so that it completely encases your rollover.
it would be much more helpful if you posted the problem so that we can take a look at it.
even multiple screenshots would be useful
