Measurement Units

I am trying to model a tree that has specific measurements such as 1 m diameter for the trunk and a height of 30 m. I am trying to figure out what the measurement units are in Tree It but I am having no luck. I was wondering if someone might be able to tell me or point me to where I can find information on this. Or is there a way to have a human reference so that I can gauge the height that way?

I was also looking for this answer. But This is how I figure out roughly about the measurement.
You can try to update to the latest version of the software, I am using Tree It 1.2.
On the viewport grid, there are numbers (50, 100, 200, 400, 800). I took this to UE4, it is equal to cm unit.

If for your case you need 30m. Since working in a really huge tree is not recommended, maybe can try to start with 3m height first. Then before export, just multiply the Global Tree Scale value by 10. So the final mesh height will be 30m.

I hope it helps. I am also still trying to figure out to use this software properly. Let me know if you have any better way to do this.