I'm not sure this doesn't qualify as a bug (bug squad: look at issue
279 and 696 for example).
Here's how to reproduce the behavior:
% The tupletNumber is printed too far away from the beam.
% A workaround exists: http://lsr.dsi.unimi.it/LSR/Item?id=646
% but do we really want to keep the attached default output?
\version "2.13.37"
\layout { ragged-right = ##f }
\new PianoStaff <<
\new Staff = "RH" {
s4
}
\new Staff = "LH"
\relative c {
\clef bass
\times 2/3 {b8 b\change Staff=RH \stemDown <e' e'>}
}
>>
Cheers,
Valentin.