Large white space at bottom of page (RH 2020)

Oh, got it, got it. 

I get it, now. Thanks, Peter!

Peter, when you say, "Second screenshot the white space is because of the window size. Reduce height and space will go away," by "reduce height," do you mean view the page on a smaller screen?  When I view that page on the my laptop screen, the large white space remains (screenshot):

SCREENSHOT:

First screenshot the TOC is filling the depth of the window so on the right there is space below text. What would you expect to see there?

Second screenshot the white space is because of the window size. Reduce height and space will go away.

Third screenshot, the left and right panels fill the window depth. The topic is not long enough to fill the centre panel.

If you look at a very long topic that will fill the depth, the "problem" will not exist. 

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If I expand the entire TOC, it looks like this:

Strangely, I have the same page open in a different tab of Chrome, and it has the larger white space at the bottom. And it doesn't go away with a page refresh:

Here's a different page that has the small white space at the bottom, even though the TOC is fully expanded:

Is that all the content of the pages shown? The slide bar suggests the TOC goes deeper and if that's the case what would you expect to be there?

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See www.grainge.org for free Authoring and RoboHelp Information