The Messenger of Allah ﷺ used to pray thirteen rak'ahs during the night ; he then offered two light rak'ahs of prayer when he heard the call to the dawn prayer.
كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي بِاللَّيْلِ ثَلاَثَ عَشْرَةَ رَكْعَةً ثُمَّ يُصَلِّي إِذَا سَمِعَ النِّدَاءَ بِالصُّبْحِ رَكْعَتَيْنِ خَفِيفَتَيْنِ