Some languages sort groups of letters as a single character. Consider the two strings: "acha" and "acia". In English they are sorted as just shown. But Spanish requires "ch" to be considered a single character that is sorted after 'c' and before 'd'. Thus the order in Spanish is reversed relative to English (that is "acia" < "acha"). This can be specified like:
"... < c < ch < d ..."
Taking case into account, you can expand this idea to:
"... < c, C < ch, cH, Ch, CH < d, D ..."