well, it depends...these things are almost never as simple as they may appear.
for this feature, is 70 a physical bound? in other words, is it possible for values to be less than 70? if not possible then the tolerance is one sided.
otherwise it's two sided.
BUT if the target is 70 and not 71.5, then Pp is calculated differently then one would do for a two sided symetrical toelrance.
If you can tell us more about the feature we can provide more specific advice...