Breaking compensatory Sawm, thinking it is the same as voluntary Sawm

Q: I did not observe Sawm (Fast) on one of the days of Ramadan because of an illness. Afterwards, I made up for that day, but at ten o'clock in the morning on that day, some guests visited me at home and I broke my Sawm, as I thought that compensatory Sawm carries the same ruling as voluntary Sawm. Then, in a religious session I heard that I was mistaken for doing so, and the preacher told me to ask Your Eminence. I hope to know the ruling on what I have done, and what I should do.

A: Whoever commences an obligatory Sawm like making up for a missed day of Ramadan or any other obligatory Sawm like that for vowing or for an oath is forbidden to break their Sawm without a Shar`y (Islamically lawful) excuse, because when one commences an obligatory Sawm, he has to complete it unless he has a Shar`y excuse. However, if one breaks that type of Sawm without a Shar`y excuse, they will not have to offer a Kaffarah but will have to make up for the days they broke whether they did so with or without a Shar`y excuse. Nevertheless, they are sinful for breaking the obligatory Sawm without a Shar`y excuse, and thus have to offer Tawbah (repentance to Allah) and Istighfar (seeking forgiveness from Allah) and resolve not to do so any more. (Part No. 9; Page No. 273) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.