> http:// ... /?val=1
> http:// ... /?val=2
...
> 
> Previously I've tried with WinHttrack writing each
> site address separately in "Web Addresses: (URL)"
> blank and I realized that I can put only about 600
It's not a count, it's the text box max size of 32K characters.
 
Create a text file via
HTTrack Help: URL number sequences
<http://httrack.kauler.com/help/URL_number_sequences>

use action=get separated files, url=file://path/to/text.txt