Как иметь модификатор multipl 'level 3' с помощью xkb

Это описано на странице руководства для bc:

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For bases greater than 16, bc uses a multi-character digit method of printing the numbers where each higher base digit is printed as a base 10 number. The multi-character digits are separated by spaces. Each digit contains the number of characters required to represent the base ten value of "obase-1".