Cisco Umbrella Custom Profile

Hi All

I am trying to deploy a Custom Profile for Cisco Umbrella as per their guide on the link below:

https://opendns.zendesk.com/hc/article_attachments/360040699791/MS_InTune.pdf

However the documentation states:

I don't really get what it is asking here, do I put the serial number in the key section or string section?

And how do I add multiple serial numbers?

Any advice would be fab

Regards