Thank you for the explanation. Now I slowly understand what you wrote last time, about how both base and meta entries are taken into account while calculating final stats. It was a bit confusing for me at that time because I was new to it, but now I understand after reading your post. Anyways, I did some tests with different "vitality" values in the individual entry while still keeping the vitality 2000 in "hardcoreNPC". In rat's individual entry, I modified the vitality to -10K(lol), and now its down to 1 HP.
