Problem with image size in epub compile

Dear fellow Scrivener users:

I will be self-publishing my first novel this coming September, and am in the midst of compiling versions for the different ebook publishing platforms. I’ve been having difficulty with the image I wanted to use as a custom separator when I compile. I got it to work for a mobi compile, and for a pdf compile, but when I compile for epub, the image comes out far larger than the image file. I tried to add a size tag (<$img:Swirl;h=15>) but no matter what number I put in for the h, the image always seems to come out the same size when I open the file in iBooks:

/Users/jackiehorne/Desktop/Screen Shot 2015-07-09 at 11.24.14 AM.png

Is there some setting that I’m missing, one that governs image size?

Any help with this pesky problem would be greatly appreciated!

Thanks in advance

Bliss Bennet