So in this case, the second codon was GCU. In this case, because we had a shift in the reading frame, the second codon is AGC, which is different than GCU. Then this one is CGC. But in this case, the third codon is UCG. Now CUG still codes for Leucine, but AGC codes for Serene and UCG codes for Serene once again. So these two codons code for the same exact amino acid.