Using a preset in Bridge to reduce the file size on a folder of images but now they aren't jpegs!

I created a preset in Bridge for exporting files with the goal of taking a folder of jpegs, reducing the file size and saving them to a new folder as jpegs. They were exported as PDF. I carefully looked at all the options in the "Edit Preset" panel and the image format is set to jpeg. Why is this happening and how do I fix it?