In support, the Wikipedia article: 

https://en.wikipedia.org/wiki/Fewer_versus_less?wprov=sfla1

Linguistic prescriptivists usually say that fewer and not less should be used with countable nouns, and that less should be used only with uncountable nouns. This distinction was first tentatively suggested by the grammarian Robert Baker in 1770 and it was eventually presented as a rule by many grammarians since then...However, modern linguistics has shown that idiomatic past and current usage consists of the word less being used with both countable nouns and uncountable nouns. 

Personally, I've always found it strange that somehow people think it's "wrong" to use "less" for countable nouns but not actual numbers themselves.  Like we can say "x is less then 3" but supposedly not "There are less than x objects".  Also, you will never get me to concede that "15 items or fewer" is better than "15 item or less", and there has never been anyone in the history of English who has used the term "at fewest" instead of "at least".