Table 2 shows the default bins for the RBS motifs. An 'x' in the middle of a motif indicates a mismatch is allowed. The right column shows the spacer distance allowed between the translation start and the motif. The leftmost column indicates the initial "score" assigned to these bins, i.e. higher bins are better. In subsequent iterations, however, these values may change, and, in non-SD-using organisms, bin 0 (no RBS) may emerge as the highest scoring.