Well, both are alpha-numeric. It's a matter of whether it looks at the full number to sort or just the first digit.
Example:
4 this
40 is
a
199 test
of
87 the
0 emergency
121 broadcast
9 system
/filter -ffct test.txt test.txt
Result:
0 emergency
121 broadcast
199 test
4 this
40 is
87 the
9 system
a
of
/filter -ffcut test.txt test.txt
Result:
0 emergency
4 this
9 system
40 is
87 the
121 broadcast
199 test
a
of
Notice that without -u, it will sort per character (121 is before 40 because 1 is before 4). With the -u, the sort will sort based on the actual number (40 is before 121).
I do agree that a better explanation in the help file would be good.
