Some audit logs arrive with masked ip address

I'm using get_events rest api to fetch activity logs.

I've noticed that part of the logs arrive with masked ip_address field.

For example this was part of the activity log(the original ip was changed for the purpose of an example):

"geo_location":{"city":"Toronto","region":"Ontario","country":"CA","ip_address":"123.123.xxx.xxx"}}

So my question is basically why part of the logs arrive with masked ips?

Thanks.