resolves #555 clarify how to preserve numbers with 3 or more digits
resolves #555 clarify how to preserve numbers with 3 or more digits

- document that numbers with 3 or more digits my be confused as a color by preprocessor
- for example, 100 is interpreted as '100' (or #110000)
- solutions are proposed

Hextremist/asciidoctor-pdf,dsisnero/asciidoctor-pdf,Hextremist/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,dsisnero/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,asciidoctor/asciidoctor-pdf