Estimating (what is most likely the case)
أَخْبَرَنَا بِشْرُ بْنُ هِلاَلٍ، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ هِشَامٍ الدَّسْتَوَائِيِّ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا نُودِيَ لِلصَّلاَةِ أَدْبَرَ الشَّيْطَانُ لَهُ ضُرَاطٌ فَإِذَا قُضِيَ التَّثْوِيبُ أَقْبَلَ حَتَّى يَخْطُرَ بَيْنَ الْمَرْءِ وَقَلْبِهِ حَتَّى لاَ يَدْرِي كَمْ صَلَّى فَإِذَا رَأَى أَحَدُكُمْ ذَلِكَ فَلْيَسْجُدْ سَجْدَتَيْنِ " .
It was narrated that Abu Hurairah said: "The Messenger of Allah (ﷺ) said: 'When the call to prayer is given, the Shaitan runs away breaking wind loudly. When the Tathwb (Iqamah) is completed, he comes back and whispers to a man in his hear, until he does not know how many (rak'ahs) he has prayed. If any one of you notices that, let him prostrate twice.'"