Having already instructed Korach and his congregation
Ramban #1 (citing Ibn Ezra): 'He already told them this earlier, only the Pasuk informs us that when Moshe instructed Korach to appear before Hashem, each man took his pan ... '.
Ramban #2: Initially, Moshe did not include Aharon, which he now did, when Korach did not answer him the first time. 2 And he now agreed, because, he figured, the fire will descend to burn the Ketores for Aharon and for all of them. Refer also to 16:17:2:1.
Why did Moshe see fit to insert the words "Chamishim u'Masayim Machtos", which he did not do in Pasuk 6?