This is typically caused by a Family registration taking place, and not a Multiple Registration.

When a Family registration is completed each participant is listed in the participant search of an event as though they were fundraising on their own independent fundraising pages.  However, they are all sharing one Family page within the event and this is why the goals combine.  For example, if Participant A has a $100 goal, and Participant B has a $50 goal, this will combine to show that the fundraising goal is $150 for the Family since they share the same fundraising page.

If you find this taking place on a Multiple Registration, please Chat with Support and reference this article.