When the cursor would be in the middle of the screen, it would be exactly on the player. The distance between the player and, for example, the right end of the screen is half the lenght of the screen.
If you move the cursor to the right end of the screen, half a lenght of the total screen gets added between the player and this end.
So the middle of the screen is always in exact the middle of the distance between the player and cursor.
In order to get an object moving to exact the same spot on the screen you simply add half of the distance between player and cursor to the coordinates of this object.