Here’s a reminder of the three interest criteria
These three criteria can be applied to our container of gold bars to define the three dimensions of the box
And for a site with 100% interest, in each dimension will be at 100%.
Now let’s imagine that half the user-base visited the site once every other day, and viewed 10 pages each visit.
Each of our three dimensions will be half filled.
Now bear in mind our third criteria says that 10 pages should be viewed per day, so if 10 pages are viewed every other day then our third criteria will also be 50%.
You can see here that our interest is now less than 100%.
In fact you can probably use common sense to see that our interest in this case would be 1/8th, or 12.5%
But mathematically multiplying the three dimensions together gives the same result.