Problem with Blizzard downloader?

I was installing WoW and i left my computer on all night for it to download and i woke up to see that the download had got 6.5gb left so it was in the playable area so i was able to play whilst it downloads. I went on for about 10 mins just to check it out etc then logged off so i could download the rest, when i relaunched the blizzard downloader it said i had 8.4gb left to download and was in the available area :S im really frustrated with this because its already taking long i dont want it to take even longer. can someone help me out with this?