1. The values in the EventTime column are timestamps estimating how many milliseconds have elapsed since Jan 1 1970 (UNIX time). What matters is the difference between them: by subtracting the timestamp of one event from that of another, you get how much time separates the two events
2. You can apply the logic I just mentioned to calculate how much time passed between when the “play” event was logged and when the “end” event was logged, ie. to estimate how long the playback lasted. The values you report are in seconds, they correspond to the in-file position of the player when the events were logged. The value of 0.000485 associated with the “play” event means that the player was at position 0.485ms in the audio file when the event was logged, indicating an infinitesimal delay between when the browser initiated playback and when PennController received the “play” event. For an audio sampled at 48Hz, 0.484ms do not even correspond to a single sample, and it is abysmally shorter than what humans perceive, so you can safely ignore this delay. The 14.069025-13.792653 = 0.276s = 276ms difference, however, is more intriguing. Are these for the same file? What format is it? wav? mp3?