If you are running macOS and your machine is out of date, you may see this pop up:

You can choose to defer it for an hour or until the next day, but only for the number of remaining days it lists on the left. After that, the notification will become more frequent. When you click "Update Device", you'll be taken to the Software Updates menu:

There you may see an OS upgrade. Do not click Upgrade Now unless you want to upgrade the entire OS, which requires administrator credentials. The update requirement is for a security update, which is hidden under the "More Info..." link beneath. It is there you'll see the updates that you need to install, which do NOT require admin credentials.