Night prayers and the number of rak`ah offered by the Prophet (ﷺ) at night, and that Witr is one rak`ah, and a one-rak`ah prayer is correct
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ عِرَاكِ بْنِ مَالِكٍ، عَنْ عُرْوَةَ، أَنَّ عَائِشَةَ، أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُصَلِّي ثَلاَثَ عَشْرَةَ رَكْعَةً بِرَكْعَتَىِ الْفَجْرِ .
'A'isha reported that the Messenger of Allah (ﷺ) used to pray thirteen rak'ahs during the night including the two rak'ahs (Sunan) of the dawn prayer.