Save for web image larger than original
I'm trying to optimize and reduce an image for web. Here are the steps I am doing:
1. Right click on the image in my finder and hit get info, the original file size is 16KB.
2. Open the image in photoshop, the image size says 401.1K (I know that image size is different than file size, and file size in your finder is a compressed version of the image, while photoshop gives you an uncompressed version and image size is expected to be larger.)
3. Bring the image into save for web. Original image size says 401K. The exported/saved versions image size is 21.23K. Metadata selection is none. Optimized is also selected (screenshot below of sizes).

5. Save image with above settings.
4. Right click on the save for web version, file size is 22KB. Right click on original version, file size is 16KB.
When I upload both versions to Wordpress, the original file is listed at 16KB and the save for web version is 22KB, so the file sizes I'm getting from my finder are consistent with the sizes in Wordpress.
How does the save for web version of the image have a larger file size than the original version? Again, I am aware that file size on your finder and image size in photoshop for one image won't be the same thing, but I still expect the save for web version of the image to have a smaller file size than the original version. What am I misunderstanding/doing wrong?
