I am using Aegisub to fix the timing of subtitles. When I want to set the end time of a line I am finding the point in the wavelength in which the person stops speaking and I am right clicking and setting it as the end time. If I press W when that line is selected then I can listen to 500 ms after the end time of the line. I am not hearing the ending echo of the end of the last word that is said in the sentence when I press W. However, when I play that line I am getting the feeling that the ending echo of the end of the last word that is said in the sentence is coming just after the line goes away. I need to add a delay at the end of the line so I hear the last word and then silence\music\sound effects when I press D in Aegisub to play the last 500 ms of a line. If I do that then the line sounds ok when I play it and the ending echo of the end of the last word that is said in the sentence is not coming just after the line goes away. Why is the problem happening?

Am I setting the end time the wrong way? In the past I used to play the movie in Aegisub and I paused the movie just after the person stopped talking and I press ctrl and 4 to set the end time. This is an inaccurate method to do it because my reflexes and how fast I pause the movie will affect the end time.