Tuplets cause incorrect duration in MusicXML

Hi,

I attached an example MusicXML which I created with MuseScore.
The example has 7:2 tuplets with 16th notes in 4/4 time, which look fine on screen.
However in the XML the beat division is 240 and the tuplets 16th are 17 duration with an added forward of duration = 1.
I'd expect in the XML a beat division of 7 and a 7:2 tuplet 16th duration = 1, or some kind of multiple of this (eg division 14, duration 2).
Is this by design or a bug?
Although a minor difference not important for the ear, it looks like an inconsistency in the XML file.

Thanks
Joe

ps I'm running MuseScore 1.0 revision 3996.