An AP story a while back described a "...hole 6-feet deep” parallel to the practice undertaken by Consumer Reports maybe a decade ago: eg, “...3-million dollars,” a hyphen application unusual at the time and perhaps distracting to some readers. It still jars me every time I encounter it

I suppose you could argue that "3-million" modifies "dollars" but the construction is or was contrary to convention

In “6-ft. holes” the hyphen is of course correct because it identifies a compound adjective; otherwise we might think there’s such a thing as a “foot hole,” and that there were six of them

But I’m confused about the rationale behind holes 6-feet deep and I hope one of your lingo-proficient bloggers can help me out here–Thank you all

dalehileman