The dining plan has nothing to do with how many days you stay. It's based on how many nights you stay. If you are staying 5 nights and you get the regular dining plan, as soon as you check in you will receive 5 TS, 5 QS and 5 snack credits per person. You then have until midnight AFTER you check out on Friday to use all of them. So if you are leaving very early on Friday, you should plan to use all your credits by Thursday. And you can't get a partial dining plan, if you stay 5 nights you must get the dining plan for 5 nights.
So you seem to have 4 days in which to use your 5 nights worth of credits, but you can use the credits for any meal, on any day you want. You may wish to plan your dining so those credits will get used.