Generally, fewer is used when a number of things can be counted (“fewer problems”) and less is used when an amount is measured (“less trouble” or “less time”). However, this is not a strict rule and there are accepted instances of less being used with countable amounts such as “250 words or less,” “3 items or less,” and especially with money (“less than $20”) and distance (“less than 3 miles”). Note that in all these cases, the things considered are often thought of as amounts rather than numbers.
Fewer*
https://www.merriam-webster.com/grammar/fewer-vs-less
“38,000 mentions”, so “less” is appropriate.
I thought it was, one less and two fewer.
It is absolutely a strict rule and Merriam Webster can fuck right off.
An entire Wikipedia page exists on this due to the evolution of use. https://en.wikipedia.org/wiki/Fewer_versus_less
Even Tesco avoided using “fewer” to keep from getting stuck in this debate.
The rule may have been codified in the 1700s, but plenty of linguistic shifts have occurred since then.
*führer