Forgetfulness during Prayer Sunan Ibn Majah 1204

Arabic hadith text
حَدَّثَنَا عَمْرُو بْنُ رَافِعٍ، حَدَّثَنَا إِسْمَاعِيلُ ابْنُ عُلَيَّةَ، عَنْ هِشَامٍ، حَدَّثَنِي يَحْيَى، حَدَّثَنِي عِيَاضٌ، أَنَّهُ سَأَلَ أَبَا سَعِيدٍ الْخُدْرِيَّ فَقَالَ أَحَدُنَا يُصَلِّي فَلاَ يَدْرِي كَمْ صَلَّى ‏.‏ فَقَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِذَا صَلَّى أَحَدُكُمْ فَلَمْ يَدْرِ كَمْ صَلَّى، فَلْيَسْجُدْ سَجْدَتَيْنِ وَهُوَ جَالِسٌ ‏"
Translation
‘Iyadnarrated that he asked Abu Sa’eed Al-Khudri

“One of us praysandhe does not know how many (Rak’ah) he has prayed.” He said: “TheMessenger of Allah (ﷺ) said: ‘When anyone of you prays and doesnotknow how many he has prayed, let him perform two prostrationswhile heis sitting.’”