One child once sold his property. The case came before R. Chiya bar Yosef and R. Yochanan...

R. Chiya bar Yosef: There is an assumption that the witnesses would have only signed after they clarified that the boy had understanding. Therefore, the sale is valid.

R. Yochanan: Since with this sale the buyer had accepted that the property should be transferred from one family to another, he must bring proof (that the young seller had understanding) as we say that the document owner has the upper hand.

Question (R. Yasa to R. Yochanan): What will you do with the words of Rebbi, who said that the document owner has the lower hand (meaning that we read it in the way that is detrimental to the document owner)?

Answer (R. Yochanan): All agree that he has the upper hand.

R. Yasa: And what do you say about the matter?

Such a case came before R. Chiya bar Yosef and he ruled that the witnesses would have only signed after they clarified that the boy had understanding (so the document owner has the upper hand) and you (R. Yochanan) said that since the buyer had accepted with this sale that the property should be transferred from one family to another, he must bring proof (meaning that the document owner has the lower hand)!

R. Yochanan replied: I didn't say that.

Question (R. Zeira to R. Yasa): Even if R. Yochanan denies that he said it, there is still a question - didn't R. Yanai say in the name of Rebbi (above in daf 153) that the document owner has the lower hand and R. Yochanan responded that it is in fact taught in an explicit Mishnah...?

Answer: R. Yochanan was merely teaching that the Chachamim follow Rebbi...but as for R. Yochanan himself, he rules like R. Yirmiyah said in the name of Rav, that the Halachah is like R. Meir.