When intervals are very small, they can be highly dissonant although they may be represented by small-numbered ratios. When intervals are very large, they may have very low dissonance and consonance.
For example, one can play almost any notes together 6 octaves apart on a piano and they won't sound particularly consonant, but they won't clash either. This runs contrary to the idea that consonance and dissonance represent opposite ends of the same spectrum [see sonance]. No rigorous adjustment for span was worked out, although normalizing all intervals to the octave between 8/7 and 16/7 is one expedient workaround.