\def\NoteNumber#1{\hbox to 15pt{\hfill\black \dostartoverprint#1\dostopoverprint}}
%\def\NoteNumber#1{\hbox to 15pt{\hfill\black #1}}
\setupfootnotes
  [bodyfont=6pt,
   textcolor=black,
   before=,after=,
   rule=off,
   numberconversion={set 2},
%   distance=-2em,
   margindistance=-2em,
   numbercommand=\NoteNumber]

\def\MyFootnote#1{\footnote{\hskip3em \dostartoverprint#1\dostopoverprint}}
%\def\MyFootnote#1{\footnote{\hskip3em #1}}


\starttext

 \startlocalfootnotes
 \vbox\bgroup\hsize=78mm\dontcomplain
 \startitemize[4]
 \item die Ausgabe erfolgt als PDF/X-4p\MyFootnote{ISO 15930-7:2008}
 \stopitemize
 \egroup
 \stoplocalfootnotes

 % footnote marker is not moved!
 \moveright70mm\hbox{\placelocalfootnotes}


\stoptext