Some, such as the Gun Violence Archive, include events in which multiple people are shot regardless of number of deaths, and so report much higher figures.
This carries a fun implication: let’s deflate the number of mass shooting by only including the deaths and not how many people are actually shot (and perhaps saved by emergency room personnel).
You don't, most people won't get the mental health care service they need after that type of event and the harm just gets ingrained in those communities.
It also ignores any lingering effects the survivors might suffer, whether physically or mentally. Just because you're alive doesn't mean you are whole.
It also encourages confusion that each mass shooting is someone trying to kill as many people as possible in a public place, when that overwhelmingly isn't actually true.
That last part is important, because our emergency responders have gotten very good at saving lives (sadly, they've had to). People will point to deaths as the only relevant stat--and it's amazing that isn't enough for some people--but it's a huge burden and cost for healthcare.
Mass shooting, not mass killing. I'd even want to know about instances of multiple, unrelated targets. If we get a string of shooters with terrible aim and nobody is actually hurt I don't consider that an improvement of our epidemic.
"If I just focus on rhetoric, all the rampant gun violence goes away! I mean, no, there is no gun violence. Regardless, everything is fine, you just have to pretend. Guns have nothing to do with gun violence, also war is peace, and I am sane in the head. I'm sure people will buy this if I just repeat it a lot."