Fewer versus less

This rule can be seen in the examples "there is less flour in this canister" and "there are fewer cups (grains, pounds, bags, etc.)

[3] The comparative less is used with both countable and uncountable nouns in some informal discourse environments and in most dialects of English.

Many supermarket checkout line signs, for instance, will read "10 items or less"; others, however, will use fewer in an attempt to conform to prescriptive grammar.

Descriptive grammarians consider this to be a case of hypercorrection as explained in Pocket Fowler's Modern English Usage.

"[12][failed verification] The Cambridge Guide to English Usage notes that the "pressure to substitute fewer for less seems to have developed out of all proportion to the ambiguity it may provide in noun phrases like less promising results".