what does iccid number printed on iphone 8 plus box means

See the following from https://www.macworld.co.uk/how-to/iphone/how-find-sim-number-on-your-iphone-3623 527/

Your iPhone's SIM number is technically called the ICCID, which stands for Integrated Circuit Card Identifier. It usually consists of 19 or 20 characters, and is both printed on your SIM card and stored inside it.

The ICCID is a unique serial number and is specific to your SIM card. It's one of the terms defined in our dictionary of tech jargon.