Hi James and Justin,
Not sure if you ever found an answer to your questions, but I figured I'd answer you 2 months later just in case (as it took me a while to figure it out! ๐
The Early bird and Last-minute discounts will only appear if you turn off Smart Pricing. Go to your Pricing settings, turn off Smart Pricing, and refresh your page. You'll first only see the "Early Bird discount" section available. To make the "Last-minute discounts" section appear, you need to set the "Early bird discount" to something (even if just to test it) and refresh the page again. In a moment you'll see the "Last-minute discounts" section appear.
And there you have it!
Cheers,
Jackie