Hi,
If the purpose is to apply a policy only to one IP address / Endpoint, you need to declare it in Policy detection.
Note: on the initial screen "Rule Type" you don't have this option, so:
1 - Go to your policy and create a new Detection Rule (Add Rule)
2 - choose Content macthes keyword (example), give it a name and insert a test Regular expre4ssion;
3 - ALSO MATCH Sender/User matches pattern -> define IP address.
4 - Delete Content Matches Regular Expression option.
This is just an example of how to declare an IP in detection. If you want to combine it with other detection method, just add the detection rule you want (therefore, detection must be Rule X AND Sender/User Matches Pattern.
Hope that helps you.
Regards,
Paulo