F.16 what exactly is cheap to copy for the purposes of passing "by value"?

F.16 says:

What is “cheap to copy” depends on the machine architecture, but two or three words (doubles, pointers, references) are usually best passed by value.

I need clarification on what the guidelines mean by "two or three words". I have two conflicting interpretations:

• 1 word == sizeof one double, pointer or reference and thus objects two or three times this size should generally be passed by value (such as string_view or shared_ptr)
• "two or three words" is the sizeof one double, pointer or reference and thus anything larger than that should be passed by reference.

I find the first interpretation more logical. Can the text be clarified? Do you accept PRs for fixing this and clarifying that the first interpretation is correct?