Dimensions vs outline

[Pierre Perol-Schneider]

Hi List,

I'm trying to understand the difference between "outline" and "dimensions":

\version "2.20.0"
\markup {
   "1234"
    \combine
    \filled-box #'(-1 . 4) #'(-1 . 2.5) #1
    \override #'(style . outline)
    \override #'(thickness . 3)
    \whiteout
    \with-outline "555"  "5" "6789"
}
\markup {
   "1234"
    \combine
    \filled-box #'(-1 . 4) #'(-1 . 2.5) #1
    \override #'(style . outline)
    \override #'(thickness . 3)
    \whiteout
    \with-dimensions-from "555"  "5" "6789"
}

Can anyone show me a clearer example?

TIA, cheers,

Pierre