The highest/worst possible average percent of non-conforming items in the process, after employing some inspection scheme. This measure is usually used in rectifying inspection, where the inspection procedure changes the outgoing rate of non-conforming items in the batch or process, relative to the incoming rate. For example, by removing the non-conforming items that are encountered during inspection. Note that this is only the worse possible average percent of non-conforming items, and therefore there is still a possibility that the percent non-conforming of a single batch will exceed this limit.
Quality isn't something that can be argued into an article or promised into it. It must be put there. If it isn't put there, the finest sales talk in the world won't act as a substitute.