As Rdl mentioned, you can see the unrarring and/or repairing process in the Par2 tab, as soon as your download is finished. The par2 parity volumes in your download are imported in your download queue as paused by default. The par2 index file however, is not imported as paused because Alt.Binz needs it to verify that your downloaded rars not damaged or incomplete.
If it turns out that (one of) your rar archives is damaged or incomplete, Alt.Binz uses the par2 index file to see which parity files it needs to download. That's why the index file is downloaded by default.
You can have the index file imported as paused as well though, by checking 'small par2 file' under NZB options in Setup. Under Par2 options in Setup, you can have Alt.Binz delete all the par2 stuff after checking and unraring.