LM 2.1.3 - bare durations

[Federico Bruni]

LM 2.1.3
I don't understand well the second sentence in this paragraph (in 
master only at the moment):

"This shorthand may be useful in other places where the rhythm changes
with an unchanging pitch, but remember a bare duration will attach to
the preceding pitch, making a single note, if only white space
separates them."

I can put more than white spaces between  the pitch and the bare 
duration:

\version "2.19.15"
\relative c' {
 c8 4. 2 |
 c8-3 \mark \default 4. 2
}

Sorry for nitpicking, but I can't translate it if I don't understand 
what it means.

Thanks
Federico