Scaling issue in workflow

For a small job where I must alter a very small piece of an existing page, I use a screen-print of that page in Axure:

  1. I copied the full page from a Chrome browser with FireShot, and before that, I have exactly put the Chrome browser to a width of 1460 pixels (with WindowResizer).

  2. pasted the copied page into Axure, where the image correctly measures 1460 pixels wide.

  3. I worked on the page within the existing width.

  4. Unfortunately, when I now preview the page in Chrome that is still set at a width of 1460, is see my new page scaling by 75%. (I.e.: when I put Chrome to ‘Scale to width’ is scales up by 1.33% which shows how the page was meant to be).

And BTW, I both tried this Page dimensions Auto and Custom web set to 1460.

Anybody an idea what goes wrong in my workflow?