RNase cleavage of the last six nucleotides is the next step following the ligation, ultimately extending the primer strand by a single base. Such cleavage allows rezipping of 6 nucleotides of the hairpin, signaled by a decrease in hairpin length of ~4 nm. Therefore, an incorporation of a complementary nucleotide is indicated by an increase in 7 nucleotides (+5 nm) followed by a decrease in 6 nucleotides (-4 nm).