A couple things that I think you miss in this explanation when reading it -
1. Its domestic only, its doesn't account for international.
2. Its based on an average of the last 5 years only. And if you remember what's happened the last 5, the whole box office has been turned on its head.
So when talking about "legs" a lot of the old rule book that people tended to use got thrown out and reset. So the averages have been out of whack because there were wide swings over the last 5 years because its a small sample size.
And here is why just using that chart doesn't work in a lot of cases in this post-pandemic world. I think we can all agree that Minecraft has been a monster of a movie this year, coming just shy of $1B it had pretty good "legs" both domestically and internationally with a fairly normal 45/55 domestic/international total split.
Well here is its chart according to Numbers -
View attachment 862371
Look at it, its "legs" according to Numbers are at the bottom of that shaded area meaning according to the site it had poor "legs" domestically during its run. But that doesn't match up with its actual domestic number of $423M domestically, which showed it actually had good legs. So it doesn't add up.
Now look at it compared to Stitch -
View attachment 862373
They look like they are tracking almost lock step with each other based on just the chart.
But.... If you drill closer and look at the daily numbers.....
View attachment 862374
Stitch has actually been tracking higher almost daily since almost the beginning, and now is $1.4M ahead of where Minecraft was at that same point. Meaning that if it continues with its "legs" it'll continue to do better than Minecraft and should bring in more domestically, ie it has good "legs".
And again none of this means anything for international as that isn't captured in that chart. And that calc you do where you take the final domestic/international of one movie already out of theaters and compare it to a movie still in theaters doesn't work as has been explained previously as well.