Here two nice links about your question: Differences Between "Wait (ms)" and "Wait Until Next ms Multiple"
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/12b2ea9ad5b265ad86256257004dd8e2?OpenDocument Software Timed Loops using Wait (ms) and Wait Until Next ms Multiple http://zone.ni.com/devzone/conceptd.nsf/webmain/E83351E12CD2D50886256B66006E4D15?opendocument Hope it help
