Which Corinthians did Paul baptise, just Crispus and Gaius or the household of Stephanus too?

In 1 Corinthians, Paul expresses his relief that very few of the Corinthians can boast that they were baptised by him. However, His statement of precisely which Corinthians he did baptise shows evidence of confusion:

I thank God that I baptized none of you except Crispus and Gaius, so that no one can say that you were baptized in my name. (I did baptize also the household of Stephanus; beyond that, I do not know whether I baptized anyone else.) [1 Corinthians 1:14-16 (NRSV)]

First Paul says that he only baptised two of the Corinthians. Then he says that he also baptised a further household. Finally, he admits that he doesn’t know whether there were still others that he baptised.