Image Size – Blask Page

Hi all,
I am running a very simple vertical gallery via a single page in Blask – see https://www.the218.com
I would like to view the images at their full size on the page.
I have uploaded images at 1200px wide and when I insert them into the page I select show at full size. However, they always show up smaller.
If I right click an image and show in new tab – the full size image is displayed.

Anyone have any ideas? Is this something I can change?

Great simple theme
Many Thanks
D

The page I need help with: [log in to see the link]