He is applying the usual trends in extrapolating out, yes. But then some trends reoccur with great consistency, so one can lay out the most probable scenarios. A summer sequel that opens to less than or about the same as the preceding film and ends up with a similar gross is pretty much a unicorn. I'd love for STiD
to turn out to be that unicorn, but the path beyond Memorial Day weekend makes that unlikely.
Edit to add: the Tuesday actual is $6,761,446 for a total of $98,446,262.