1. Rav: The Tana Kama agrees that when there is an Amaltera, the Korah may be more than 20 Amos high.
2. The Gemara discusses why the Tana Kama says that the Korah must be placed less than 20 Amos high.
3. The Gemara discusses the cases of a Korah and Sechach of a Sukah that are partially above and partially below 20 Amos.
4. Rabah bar Rav Ula and Rava disagree about the law in the case above (#3).
5. Abaye: The Amos with which the laws of Sukah and Mavoy are measured are small Amos, while the Amos with which the laws of Kil'ayim are measured are large Amos.
A BIT MORE
1. The Gemara later discusses various opinions about the exact definition of an Amaltera. According to all opinions, an Amaltera is something that attracts attention so that people notice the Korah despite the fact that it is more than 20 Amos above the ground.
2. For example, Rav Nachman bar Yitzchak says that people must be able to see it and realize that the inside of the Mavoy is a Reshus ha'Yachid and not a Reshus ha'Rabim.
3. There are two versions of Rabah's opinion on the matter. One version says that such a case is valid for a Mavoy but invalid for a Sukah. Another version says that it is invalid for a Mavoy and valid for a Sukah.
4. Rabah bar Rav Ula says that both are valid, while Rava says that both are invalid. (Neither one agrees with either of the two versions of Rabah above (#3).)
5. The Amah for the laws of Sukah and Mavoy (Eruvin) is comprised of 5 Tefachim. The Amah for the laws of Kil'ayim is comprised of 6 Tefachim.