In a book on jazz harmony in Russian I have noticed the term 'open interval'. Example 57 says that interval -9 in the right arrangement is 'open interval' (in this case it's bad). The left arrangement is 'better' (smth which looks like 67 is in fact 'major 7th' in Russian notation).
My question is: Does 'open interval' here mean that one of the notes which form the -9 interval is THE HIGHEST of all the four notes, i.e. openness implies there is nothing above Bflat here?