ODF 1.2 Part 1 16.27.27 <number:text-content> underspecified

Setion 16.27.27 states that

"The <number:text-content> element contains any variable text content of a text content."

However, the schema specifies that <number:text-content> is <empty/>, meaning that it has no attributes an no children (including text).

It appears that, unlike <number:text> the <number:text-content> does not contain anything. Rather, it seems to be a marker for or about something. This needs to be explained.

For example, here is an use of the element as a child of a <number:text-style> instance in a prominent and presumably-correct implementation of ODF:

<number:text-style style:name="N5136" number:language="en" number:country="US">
<number:text></number:text>
<number:text-content/>
<number:text></number:text>
<style:map style:condition="value()>0" style:apply-style-name="N5136P0"/>
<style:map style:condition="value()<0" style:apply-style-name="N5136P1"/>
<style:map style:condition="value()=0" style:apply-style-name="N5136P2"/>
</number:text-style>

Q1: What is a consumer expected to understand about that element? Does it have something to do with the presence of style:map elements and their style:condition expressions?

Q2: How does a producer know when it is appropriate to provide that element (here or elsewhere).