You can use the "Add User Agents/Bots to Ignore/Not Log" option in the Security Log to ignore by User Agent. This is a known issue that has something to do with...
@2x images are used in Responsive website design and specifically by Retina, which automatically resize images based on pixel density (pixels per inch/PPI) for devices....What I assume is happening is that the Retina script on your device is doing several different things and one of those things is being blocked by BPS. Since the images display correctly when viewing the site from a desktop interface and from a mobile device you can disregard these Security Log entries.
So you can either ignore these log entries by adding the User Agent or just ignore them in general.