\starttext

\section{First line shifted to the right by a bit less than 2pt}

\setupTABLE[offset=0pt, frame=off]
\setupTABLE[r][1][bottomframe=on, rulethickness=2pt]
\bTABLE
\bTR\bTD bla \eTD \eTR
\bTR\bTD bla \eTD \eTR
\eTABLE

\section{Workaround}

\setupTABLE[offset=0pt, frame=off, rulethickness=0pt]
\setupTABLE[r][1][bottomframe=on, rulethickness=2pt, loffset=-2pt]
\bTABLE
\bTR\bTD bla \eTD \eTR
\bTR\bTD bla \eTD \eTR
\eTABLE

\stoptext

