question #3 Sahih Muslim 1146a, Book 13, Hadith 193 : What is the significance of completing missed fasts before the next Ramadan begins?

I heard ‘A’isha (Allah be pleased with her) as saying: I had to complete some of the fasts of Ramadan, but I could not do it but during the month of Sha’ban due to my duties to the Messenger of Allah (ﷺ) or with the Messenger of Allah (ﷺ).