The difference in the text found in the CMS QRDA EP & HQR 2015 Implementation Guide and the text found as part of the rule error description are different and this is causing some confusion between the guide and the rule.
In the CMS QRDA EP & HQR 2015 Implementation Guide (pp.30) we have the following;
The CDA standard requires an author with an identifier to represent a person or device that have created document content. For a given document, there may be multiple authoring individuals and/or devices. Authors may also be described in other header elements, depending on roles.
13. SHALL contain at least one [1..*] author (CONF:18156) such that it
The author/time value represents the time when the document was last edited. When there are multiple authors, the first author time usually correlates with the effectiveTime of the document, which is when the document was generated.
a. SHALL contain exactly one [1..1] time (CONF:18158).

In the Lantana rules file (.sch) we have the following;
<sch:assert id="a-77-18156" test="count(cda:author[count(cda:assignedAuthor[count(cda:representedOrganization[count(cda:name) > 0])=1])=1][count(cda:time)=1]) > 0">The CDA standard requires an author with an identifier. In addition, the QRDA Category III document type requires that the author be declared as a person or a device. The document can be authored solely by a person or by a device, or the document could be authored by a combination of one or more devices and/or one or more people.
SHALL contain at least one [1..*] author (CONF:18156) such that it SHALL contain exactly one [1..1] assignedAuthor (CONF:18157). This assignedAuthor SHALL contain exactly one [1..1] representedOrganization (CONF:18163). This representedOrganization SHALL contain at least one [1..*] name (CONF:18265). SHALL contain exactly one [1..1] time (CONF:18158).</sch:assert>

Please try to make this rule text and the documentation match. It almost looks like an error in the documentation because the rules appear to be interrupted by text.

Should this be like the following modification example?
8.1.2 author
The CDA standard requires an author with an identifier to represent a person or device that have created document content. For a given document, there may be multiple authoring individuals and/or devices. Authors may also be described in other header elements, depending on roles. The author/time value represents the time when the document was last edited. When there are multiple authors, the first author time usually correlates with the effectiveTime of the document, which is when the document was generated.

SHALL contain at least one [1..*] author (CONF:18156) such that it
a. SHALL contain exactly one [1..1] time (CONF:18158).
b. SHALL contain exactly one [1..1] assignedAuthor (CONF:18157).

See attached JIRA Ticket Description with formatting for clarity.