It has been turned out that the detection and visualization of the play time of a media file is technically realized by several applications in several ways.
To see the "true playtime" we would need to have an integer number measured in Milliseconds.
Some applications simply neglect or cut off or round down the true play length to the base second.
Some applications round up to the next full second.
I prefer the round up method, because the time duration of a second, which has already begun and is partly used or filled while miroseconds of data, ends with the starting point of the next second.
See also:
Exporting length to CSV file
DD.20111009.0714.CEST