Board Thread:Questions and Answers/@comment-25139420-20140707212930/@comment-5334617-20140707213736

So far as I can tell,  will wait until the beginning of the  th frame after the last   or. If  frames have elapsed already,   will take no time at all. By contrast,  will wait until the beginning of the  th frame after the beginning of this   command.

So, if you have a, then you do a lot of calculations that takes, say, 4.5 frames to complete:    will take no time,   will take no time,   will wait until the end of the current frame,   will wait 1.5 frames,   will wait until the end of the current frame,   will wait 3.5 frames.