Need assistance with extension delivery

[sendrebiebs]

It's already 1 January. So i got an order recently, for some misunderstanding we have to extend the date to 4th January. Fiverr has given days to select for extension such 2 days 6 days and so more. There in the extension section it was already selected with "6 days" but was written something like "buyer will expect with in 'january 2" not exactly the words, but meaning same. So i chose 8 days then it shows "4th January" I'm afraid of what's going on. I wanted to use some clarification on this. Thank you!