If the download fails via the dashboard, you can download the 650.5 MB file from the official PlayStation support site onto a USB drive.
If your console is in "Rest Mode" with auto-updates enabled, it usually downloads this 650.5 MB file in the background. Why 650.5 MB? Download 650.5 MB
If you are seeing this specific file size and having trouble: If the download fails via the dashboard, you
Improving system performance and software stability. Download 650.5 MB
For many years, PlayStation 4 firmware updates have hovered around this specific size (between 400 MB and 700 MB). This is because the console downloads a "standard" update file that replaces or patches core operating system files rather than downloading the entire system software (which is usually over 1 GB). Troubleshooting the Download