It is annoying but I believe (and I hope someone will correct me if I'm wrong) but sorting text first looks at the length of the value to be sorted by and then by it's value.
So, if you had 001, 010,, 01c, 100, 1000a, etc. instead of 1, 1a, 2a, 10c, etc. youi'd get the sort to end up the way you wanted it to.
Does thi smake sense???
Hope it helps.
this problem is easily solved by creating a new calculation field with calc:
Right ( "0000000000" & Filter ( Scene numbers ; 1234567890 ) ; 10 ) & Right ( Scene numbers ; 1 )
and sorting by that new field.