Issue:
Permutation of 4 is 24, not 16.

Document link:
https://github.com/less/less-docs/blob/484055f839c15aba1ec660fc1e068984c3dccef6/content/features/parent-selectors.md

Document lines:
& can also be used to generate every possible permutation of selectors in a comma separated list:
p, a, ul, li {
....
}
This expands to all possible (16) combinations of the specified elements:

The above document lines say permutation of 4(p,a,ul,li) is 16 which i think is not correct.

Proposal:
Instead of using the word "permutation", we can use something else. My suggestion would be to frame the sentence to something like
"& can also be used to generate every possible combination of selectors in a comma-separated list:"
and
"This expands to all possible combinations of the specified elements:"