Greetings,

We would be more able to help if you send us a specific question about what Rashi says. In summary, Rashi is explaining as follows: Abaye (on 24b) asserts that one is punished with Malkus for benefiting from Kila'i ha'Kerem even in an unusual manner (she'Lo k'Derech Hana'asan). The Gemara challenges this from a Beraisa which says that the Isur of Hana'ah of Basar b'Chalav is learned from the Isur Hana'ah of Kila'i ha'Kerem. The Gemara asks that we should not be able to learn the Isur of Hana'ah of Basar b'Chalav from Kila'i ha'Kerem because Kila'i ha'Kerem has a unique Chumra which Basar b'Chalav does not have -- it was never, at any point in time, permitted, while Basar b'Chalav was, at one point in time, permitted (i.e. before the Basar and Chalav were mixed).