Why you might have a different count of images in Photos in different places<article>
<section class="page">
<p>With iCloud Photos enabled, your pictures and videos sync across all connected devices via iCloud, including retaining a set that’s accessible at icloud.com. However, readers frequently write in that they see a different count of media in the Photos app on an iPhone or iPad and Photos in macOS. The reason can stem from a couple of causes, but I have some bad news at the bottom of this article.</p><p>Photos for macOS has an option to either copy media into its library or reference a photo or movie from where it sits on a drive. iCloud Photos, however, will only sync media copied into the library and under control of Photos; referenced images are ignored. The setting to choose copy versus reference is in
Photos > Preferences > General as “Copy items to the Photos library.” If unchecked, anything you import via a menu item or drag into Photos to import will effectively only maintain a thumbnail of.</p><p class="jumpTag"><a href="/article/3537548/why-you-might-have-a-different-count-of-images-in-photos-in-different-places.html#jump">To read this article in full, please click here[/url]</p></section></article>
Source:
Why you might have a different count of images in Photos in different places