The documentation for GetClassSortKey says
* Concatenates class and item part.
* Converts to uppercase.
* Removes leading and trailing whitespace and '/'
* Separates alphabetic prefix from the rest of the call number
* Splits into tokens on whitespaces and periods.
* Leaves first digit group as is.
...
this means that callnumbers
9.1 => 9_100000000000000
80.1 => 80_100000000000000
700.1 => 700_100000000000000
when sorted ascending by cn_sort
700.1 => 700_100000000000000
80.1 => 80_100000000000000
9.1 => 9_100000000000000
Shouldn't these be zero padded to 3 digits, so that they sort as follows?
700_100000000000000