That the Prophet marked his Budn on the right side and the blood flowed down and marked it.  

أَنَّ رَسُولَ اللَّهِ ﷺ أَشْعَرَ بُدْنَهُ مِنَ الْجَانِبِ الأَيْمَنِ وَسَلَتَ الدَّمَ عَنْهَا وَأَشْعَرَهَا