It looks like you're running both Lightroom and Photoshop at the same time. It looks like Adobe recommends 16GB for Photoshop as well. Please remember that system requirements refer to the free memory available, not the installed memory, and you need to stack this number.
Let me go through an example:
- macOS Big Sur requires 4GB of memory to run
- Lightroom and Photoshop both require 8GB memory to run, but both recommend 16GB be available
So if you want to run Lightroom and Photoshop at the same time, you will require at least 20GB of memory in your machine. If you want it to run optimally you should have at least 36GB of memory.
Based on your screenshot, your usage of the applications is currently consuming 19GB of memory, so the math is fairly on point. Unless you are able to upgrade your memory, I'd suggest not running Lightroom and Photoshop at the same time.