Hmm, this is like having 200 pixels / inch but expressed as cm / inch (200 * 2.54 = 508).
In the PM Files preference, do you have the box checked to "Add Photoshop resolution info to Camera JPEGs during IPTC update"? What is your preference for Resolution units (pixels per inch or pixels per cm)?
What variable are you using to display resolution (PM has three variables: {resolution}, {resolutioninches}, an {resolutioncms})?
Try unchecking the "add resolution" box if you have it checked. This setting is mainly for "camera JPEGs" which means files that are straight from a camera where the resolution may not be properly set (e.g. a 16 megapixel image at 72 DPI is quite a large print size). Remember, PM isn't changing your image dimension, just the resolution info that is used when the photo is actually printed (and of course this can be and should probably be overridden during printing).
--dennis