Currently, the number of tasks to display on each page of results in the table are 10, 20 or 40.

Allow to choose in a wider range. n values.

Workaround

Download and use the Source Editor Plugin, it is free.

You will see, after installing, that when you go to the editor mode of a page, in the right upper corner, you will find < > option, click on it, and you will see something similar to:

....
<ac:structured-macro ac:name="tasks-report-macro">
          <ac:parameter ac:name="spaces">BSP</ac:parameter>
          <ac:parameter ac:name="status">complete</ac:parameter>
          <ac:parameter ac:name="assignees">
            <ri:user ri:userkey="2c9682654373c47f014373caa68a0003"/>
          </ac:parameter>
          <ac:parameter ac:name="spaceAndPage">space:BSP,page:2555905</ac:parameter>
          <ac:parameter ac:name="pages">2555905</ac:parameter>
          <ac:parameter ac:name="labels">meeting-notes</ac:parameter>
          <ac:parameter ac:name="pageSize">10</ac:parameter>
        </ac:structured-macro>
....

These are the macro parameter, and you can manually change the <ac:parameter ac:name="pageSize">10</ac:parameter> to 5 and save it. It will now only show 5 tasks. But, first, you need to choose the parameter in the macro, while editing it (in editor mode), for it to show in the source of it.