Marie2263, you have a package of 11 credits. You might need more credits in order to download the size/format you want.
The 11/15/30 etc credit package allows you to download a maximum of 11/15/30 etc. images if you download images that cost 1 credit each. These would be the level 0 images at the smallest size. Our image prices differ according to the image size and level and they vary between 1 and 19 credits for a maximum size, maximum level file. For a complete list of prices, check the table here.
Most of our database is made up of low level images, with level 0 being their vast majority. You can set your search to return only low level images by using the advanced search. The price filter should be available once you hit the advanced search button.
In order to see which images have been charged in your account and how much you paid for each, please access the download archive in your My Account area here or the upper right corner of the screen.