Day_2 Assignment_5 - Unclear Question : Requesting an explanation

Ankit is in maze. The command center sent him a string which decodes to come out from the maze.
He is initially at (0, 0).
String contains L, R, U, D denoting left, right, up and down.
In each command he will traverse 1 unit distance in the respective direction.

For example if he is at (2, 0) and the command is L he will go to (1, 0).