Length sorts as Text, not Numeric

[ohrenkino]

%_length% represents the formatted output - which is an alphanumeric string more or less.

To get a numeric treatment set these properties in the column definition:
sort by: %_length_seconds%
numeric: ticked.

Also see this fixed bug:

[F] Sorting on %_Length% field doesn't sort correctly

No need to parse seconds Just leave %_length% as before and enter %_length_seconds% at Sort by. Also make sure that you tick the Numeric checkbox as dano suggested.