Abu Zur'ah (may Allah have mercy on him) said: In my view the meaning of this hadith is that what you give today as three divorces, they used to give as one divorce in the time of the Prophet (peace and blessings be upon him), Abu Bakr (may Allah be pleased with him) and Umar (may Allah be pleased with him).
(b) Abu Yahya al-Saji (may Allah have mercy on him) said: When he says to a virgin: You are divorced, you are divorced, you are divorced, it was one divorce; then Umar (may Allah be pleased with him), being strict, counted it as three.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14984