Hey Paul, if you could send me a link to the page you’re working on I can give you a more definitive answer. But my first guess from the video is that the explicit height setting of the boxes means they don’t fill the full height of the grid tracks you’ve defined.
You can probably overcome this by setting the height property to 100% via the ‘All’ tab. But again, I would need to check the page to be confident in my advice.
P.S. you can turn on the grid highlight feature to help diagnose issues like this. There is a button to the left of the grid control area.
