> httrack -O "temp"
> <http://www.httrack.com/html/index.html>  "-*[>20]"

I use 3.32 and got the same results. With:
-O ".\temp" -Z "-*[>20]" -v
The debug said it was rejecting everything because of the filter.
Also tried -"*[>20]" and -*[^>20] with no success.

Looked at the httrack command guide and it said:
 *[< NN]  	 size less than NN Kbytes
Notice the space between the angle and the number.