To paraphrase a former President: that depends on the definition of "have".
What if you "have" it, but can't use it? Do you still "have" it?
It's not like you are tossing a sack of potatoes on a scale.
Hard drives are shipped with certain areas roped off and not available for use. Who knows what tool X measures? "All" of the drive? Those portions available to the consumer following an ordinary format? Those portions available to the consumer plus the portion set aside to replace failed portions of the disc? Or a fourth or fifth or sixth combination of the sub-segments that make up "all" of the disk?
A drive engineer could probably give you all of the various possibilities. I can't. But I don't agonize over it.