Rashi and Ramban: "Korbanam" refers to the bull of the Olah and "Chatasam", to the goat of the Chatas.

Ramban #1: To stress that, in spite of the severity of the sin, since it was performed be'Shogeg and they brought their Olah and Chatas, they deserve an atonement.

Ramban #2 (citing R. Yashiyah ¹ in the Sifri): If one tribe sinned following a ruling of its Beis-Din, and other tribes followed suite, they are all subject to bring an Olah and a Chatas.

Ramban #3 (According to Kabalah): The Torah inserts both "la'Hashhem" and "Lifnei Hashem", the former, corresponds to the Midas Rachamim; the latter, ² to Midas ha'Din ³ - which Chazal sometimes describe as 'Hu u'Beis-Dino'.

Zevachim, 41a: "Chatasam" refers to the Se'irei Avodas-Kochavim, and "Shig'gasam", to the Par He'elam Davar shel Tzibur, ¹ (to which the Torah is comparing it), ² and Chatasam al Shiggasam" implies that regarding the burning of the Emurim, this Chatas is equivalent to all other regular Chata'os.

Ramban and R. Bachye: They brought the Olah to the Shem Havayah (Midas Rachamim) ¹ and the Chatas before the Midas ha?Din ? corresponding to ?Hu u?Beis Diyno?. ^{2 3}