It was traditional 30 years ago to describe web site traffic levels in terms of hits per day, perhaps because "two hundred thousand hits per day" sounds more impressive than "2.3 hits per second". Consequently a lot of us have some kind of intuition for what kind of service might need to handle a thousand hits per day, a million hits per day, or a billion hits per day.
As other commenters have pointed out, peak traffic is actually more important.
As a comparison between implementations it can be useful. It is more than a big enough number that, if the test was actually done over a day, temporary oddities are dwarfed. If the test was done over an hour and multiplied then it is meaningless: just quote the per hour figure. Same, but more so, if the tests were much shorter than an hour.