What is the meaning of a discrepancy in the text of the same Hadith from one chain of narration to another, given that both are accepted, an example of which is the difference in the number of rak'ahs for the emphasized supererogatory prayers (Sunan Mu'akkadah) between sound Hadiths?

The variation in the wording of a hadith is due to several reasons, among them: that each Companion narrated what he witnessed, or that the narrator forgot some of the wordings. It is not possible to answer every two differing hadiths with a single answer; rather, it depends on the context and circumstantial evidence. Regarding the differing hadiths concerning the emphasized Sunnah prayers, Ibn Hajar mentioned that the discrepancy between the hadith of Ibn Umar (two rak'ahs before Dhuhr) and the hadith of Aisha (four rak'ahs) can be understood as each Companion describing what he saw, or that the Prophet, peace and blessings be upon him, sometimes prayed two rak'ahs and sometimes four, or that he prayed two rak'ahs in the mosque and four in his home.