Please, let me understand...

I run a cmq like this httrack -i "www.mysite.com/eng/pages/default.aspx" -o
C:\sitebkp -argumentstring.

In the folder sitebkp I already have a COMPLETE site structure. With the new
call, httrack stores in C:\sitebkp\eng\pages a file called default-1.aspx.

Can you explane me why?