Hi Enriqueta,
Chances are it won’t be exactly 300ms, because performance varies with different hardware and software configurations. Timer elements periodically check the browser’s current timestamp, usually 60 times per second, generally matching the display refresh rate. So running a 300ms timer will effectively take between 300 and 316ms under normal circumstances.
Yes, the EventTime values are also expressed in milliseconds, and subtracting two of them will accordingly tell you how many milliseconds passed between the two reported events.
Jeremy