moodle/lang/en/help/coursenumsections.html

<p align="center"><b>Course Number of Weeks/Topics</b></p>

<p>This setting is only used by the 'weekly' and 'topics'
   course formats.</p>

<p>In the 'weekly' format, it specifies the number of weeks 
   that the course will run for, starting from the 
   course starting date.</p>

<p>In the 'topics' format, it specifies the number of topics
   in the course.</p>

<p>Both of these translate to the number of "boxes" down the 
   middle of the course page.</p>