Fifth grade teacher some decades ago told me something quite smart I will never forget, if you are in doubt about something apply math to it, math does not lie and never fails, 2+2 will add to 4 every time.
Don't recall the actual numbers, 40 million rounds? NOT BILLIONS but the thing about DHS ordering oodles of ammunition has been around for some time and taking in account first of all that this huge orders are done in such amounts both to secure an ongoing supply down the line and perhaps even a "better price", a GIANT truck convoy does not back up with millions of rounds at once, takes years for this "order" to materialize so you factor this in and all of their employees, that need to practice and qualify with firearms and the amount is more than reasonable.
DHS ia a giant umbrella with lots of federal agencies under it.
Of curse when the irresponsible media does not show the entire picture and just sells us a "blurb" with them huge numbers next to a government agency in bold letters it feeds our need for drama and there we go like the proverbial Pavlovian frog legs!
Some say that when in doubt the first thing that comes to mind is most often the correct one, when there are empty LGS all over the country because of an ongoing "buying frenzy" by old and MANY NEW gun owners first thing that comes to mind is that this "buying frenzy" includes ammo as well, more so in the most popular calibers...