Upvote:2
Your visa has two numbers.
So they gave you the option to stay one day longer than originally planned, or to postpone the entire trip, both arrival and departure, by up to two weeks.
Imagine you have a visa with 10 days duration and a validity from January 1st to January 13th. Then your options are to visit either January 1st to 10th, or January 2nd to 11th, or January 3rd to 12th, or January 4th to 13th.