If the husband confirms that he had uttered the word of talaq thrice then all the three talaqs occurred. If the husband says and thinks that by saying talaq three times only one talaq occurs, it is his ignorance. The ruling of Shariah is that if the husband gives three talaqs to his wife (with whom he met in privacy and had physical relation) in a single utterance or in three separate utterances then talaq mughallaza takes place and the relation of husband and wife comes to an end entirely. In future they cannot do nikah without a Shariah halalah. The ruling is proved from the holy Quran, Hadith, consensus of sahabah, Tabi’een and Ayemmah.
Allah knows Best!
Darul Uloom Deoband