@GeoffGI made a mistake in the above post!
If you look at it closely you will see that it is showing the "ACTUAL" and of course that is correct since I haven't spent anything on fuel in December (especially in November!), and I don't have any reminders on that category.
When I just tried it I get this result. I have yet to spend anything on fuel this month, but it came up with $94. Which as it turns out is the average amount spent over the last 12 months.What it seems to be doing is using the exact numbers for the months that already have been past, and then the 12 month average for the future months (or at least in this case December). Now note that when you create a budget in 2020, you are creating a 2020 budget, not a 2021 budget (which you will find out next year when pull up the budget and it wants to extend it into 2021). You can also extend the budget now by selecting this button to go into 2021. And that will give you this dialog, and I picked the second one But if you are doing this now, clearly you don't have all the exact values for December.
Its result is "different".
The 30 is the number I put in as the existing budget before extending it as a test.
It used that for December 2021 even if I set my system date to 12/31/2020.
BTW if you do nothing and open the budget in 2021 you will get this prompt:
And as it suggests it already created the budget and it does is use the first choice on the above dialog and just use your 2020 budget numbers.