the total number of *valued* facet results. Total = other() + terms (but doesn't include
the number of results that couldn't be faceted, missing the adequate value. Not matter how many more
buckets are added to the original facet, these result won't ever be included in one.
the number of results that could have been faceted (because they have a value for the facet's field) but
weren't, due to not having a bucket in which they belong. Adding a bucket can result in these results being faceted.