Nvm, figured it out.
<representedOrganization>
<id extension="99998899" root="2.16.840.1.113883.4.6"/>
<name>Neighborhood Physicians Practice</name>
<telecom value="tel:+1(555)555-5000" use="WP"/>
<addr>
<streetAddressLine>1002 Healthcare Drive</streetAddressLine>
<city>Portland</city>
<state>OR</state>
<postalCode>97266</postalCode>
<country>US</country>
</addr>
</representedOrganization>
from the <author></author> section. It's confusing because none of the example files (that "pass" the validator) have this section in it.