The only thing I understood... spoiler to save you watching it

...was the title, eventually.

And while the title jokingly tries to explain why the majority of viewers won't get it, and I grudgingly gave it a couple of stars for that, it is a tremendous conceit to base 100 minutes of nonsense on that 'premise'. (I have only right now got the significance of the running time!)

There is a kind of focus group, or more likely studio execs, who come out of a screening of the film at regular intervals and comment on how the film doesn't make sense. Someone says that the director's intent was to make a film that you had to be 100 years old to understand. Hence R100 (restricted to 100 and over). The group point out that it will have a limited audience, with there not being many 100 year olds, and then how many of them can get to the cinema?