The dimensions for the device silhouettes should match the pixel resolutions for particular models of the device. For the iPad silhouette, the #pixels inside the silhouette should match the #pixels on an actual iPad1 (whose screen is 1024 x 768). However, the silhouette might appear bigger on your screen than the real-life device because of different pixel resolution. For example, if your desktop screen has 100dpi, and the device has 132dpi, then the device silhouette in Maqetta will be 132/100 times bigger, even though it is representing the same number of pixels.
If your operating system has an option to use higher display resolution, then everything will shrink on your desktop screen, including the Maqetta silhouettes.
We have an issue in Maqetta to allow the user to zoom in/out in the page editor (
https://github.com/maqetta/maqetta/issues/142), but when we last looked at that issue, the browsers had too many bugs around scaled content, so the zoom in/out feature in the page editor was never implemented.
Jon Ferraiolo