SV - Questions about box legendaries

[jacksonf]

Well, I've read that Koraidon/Miraidon have fixed IVs but I'm confused about it. From what I gather, the Miraidon we get should be Modest with four perfect IVs and Electric Tera-Type but I got a Quirky one with four perfect IVs, the other two at 28 and Dragon Tera-Type. I don't think I'm that lucky to get 28 twice at random, so... My questions are:

Is the nature fixed too or it is random? What about the not guaranteed perfect IVs? I've seen screenshots of 25 but never 28. And why is mine Dragon Tera-type?

I mean, I'm not complaining; 31/31/28/31/28/31 is a beast, I can mint the nature and change the Tera-type if I want to. But I really want to know how it works.

Spoilery question ahead, finish the game first:
 

Spoiler

And what about the second one, how does that one work? Am I getting them mixed and this is the one with Modest nature, four perfect IVs plus two at 25 and Electric Tera-Type?

Thanks in advance for any answer.

Edited December 16, 2022 by jacksonf