The times in the \move tag are specified relative to the subtitle line itself, not absolute.
You need to make the subtitle line have the start and end times match when you need it to be visible on screen.
The times in the \move tag then are milliseconds after the start time for the line.
You can also use the movement tool to help set it up:
First click (1) to go into positioning mode, then click (2) to go into movement mode. (Movement mode is a sub-mode of positioning mode, so you need to go into positioning first.)
You can then move the start and end points for the movement. When you move the start point, the start time for the movement is also set to the current video time, and likewise when you move the end point, the end time of the movement is set to the current video time. So, you go to the frame where the movement begins, move the start position to the right place, then you go to the frame where the movement ends, and move the end point to the right place.