The gemara brings three different tannaitic sources that contradict Rav Papa who holds if the breach is equal to the standing part, it is considered a partition. One of the sources is resolved and then brought as a contradiction for Rav Huna's position. In the end the halacha is determined like Rav Papa, even though one of the sources brought clearly contradicts, because as seen in Eruvin 15, our mishna fits better with Rav Papa. The mishna discusses putting up "flimsy" partitions made up of horizontal ropes or vertical posts using laws of levud to allow it (less than 3 handbreadths in between each). The mishna was discussing a case of a caravan, presumably with a lot of people. There is a debate in the mishna if that case was chosen specifically because only for many people is it allowed or is it permitted in all cases. Rav Hamnuna asks a question regarding a horizontal wall if it is solid more than breached, does that work? Abaye answers it simply from the mishna and comments on the details that show that it only works if the ropes have thickness to them - if they could be thinner, it still could have worked using the principle "standing more than breached" - since it doesn't say that, it must not be the case. The gemara rejects his suggestion of using thinner ropes as they explain it could not work halachically as he suggested. The gemara brings two other suggestions regarding what exactly Rav Hamnuna was asking. The gemara questions Rabbi Yehuda approach in our mishna that the leniencies in the mishna are only for caravans - didn't he say elsewhere that it works for individuals?