Documentation: broken link
I post in this section, but I'm not sure this is the right place for documentation issues.
The link to https://www.imagemagick.org/Usage/basic/#page seems to be brokenLayer Canvas/Page Offsets
The composition of Layered Images use a very different philosophy. All the images (as many as you like) are treated equally in the order given. They all have a "-page" or Page Offset that position each image's top-left corner relative to a virtual canvas 'origin' (the default offset) but without gravity.
To process multiple images a new background image is generated using the current "-background" color with a size that is dependent on the operation being performed. This is assumed to be the 'destination' image (canvas). ALL the images are composited onto this new canvas one at a time in sequence.