Early in a project, people stick to some heuristic, like using small z-index values like 0, 1, 2, 3... etc. But this has drawbacks because you can't add new z-index items in between without also shifting everything with a higher z-index

Using z-index values with a gap is a better bet. 0, 10, 20, 30, etc. Of course, you are limited to only a few items in between the original. You've also lost an expectation of ordering in the values.

Larger gaps make more sense, as long as you don't exceed the size of signed integers ±2147483647.

The author of the post mentions how floating point has a similar problem in the amount of floating point precision you can wring out before you end up with rounding errors.

The true crux of the problem is one of items related to one another, in other words it's a graph problem. I want these items to show up underneath these other items.