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It's between 11 and 12.

More precisely: it tries a very high ratio, 97%, and then it steps it down until the file size is under 4 megs (but never goes under 94%). This way, cleanly processed files (which will compress well) are given high-quality compression, but noisier ones (which won't compress as well) are slightly lower to give them a reasonable file size.

The files are also resized to a max of 3500x3500.