No, it's not the usual thread about OMG my CV's not increasing after 30$ should I call the police?!?!?!?! =D

I posted this as a comment, then I realised it was probably best to give it it's own topic. So here it is, pasted straight from the (now deleted) comment (if you don't want to read it, I give a summed-up version at the end, and you won't miss anything XD):

I'm quite sure I understand how the system explained above works (note: talking about the CV system, obviously), but a few strange things have happened recently with my contributor value. Before anything else, let me point out a few things, just to be clear: a) I'm not complaining, whining, crying or any other synonym, I'm just confused and wondering if updates have been made, or if I missed some important information not included in the above post; b) I don't mind the contributor value too much, but since it's there, I find it slightly annoying that it (apparently, at least) plays tricks on me. =P
So, my situation is like this: I had a CV of about 250$ last month after a few giveaways. When I checked a few days later, my CV had decreased to around 230$. I found it slightly strange, but after some reasoning I assumed it was because I had given away a few bundle games that hadn't yet been marked as such at the time of the giveaway (due to the slight delay between a bundle being created and the bundle list being updated, most likely). I created another, non-bundle giveaway, and my CV increased by the exact amount of the game; once again, I found this strange because, like most people, I have a lot of bundle giveaways piled up, so I expected the CV to raise by 120% the value of the game. Still, I assumed that my bundle-value was now less than 20% my CV (as strange as that seemed, admittedly). Therefore, I expected that my next bundle giveaway would raise my CV a little; it didn't, and at this point I ran out of explanations.
Today, another annoying thing happened (or rather, I noticed it today, not sure when it happened): my CV, after my latest giveaway, was around 250$ (again). I went to create a further giveaway a few minutes ago, and noticed that my CV is suddenly 215$; somehow, I 'lost' 35$. As I said above, I don't fret excessively over my contributor value (though I do track it scrupulously, as you can see XD), but I'd like to know whether this is a bug of some kind, whether I somehow did something wrong that led to it being reduced, or whether there's a rule I'm not aware of that explains what seem like arbitrary cuts.
Sorry for the long post, and thanks to anyone who will take the time to read and answer it!

As an added note, I re-calculated by hand (well, with the aid of a calculator) my CV, based on my giveaways.

SUM FOR PEOPLE WHO DON'T WANT TO READ ALL THE ABOVE (I perfectly understand)

My CV as displayed by the website doesn't tally up with my CV as calculated by me five minutes ago, based on the rules described. My official value is 215.92$, according to the website; according to my calculations, it should be 264$ (or, to be exact, 263.xyz). The total value of my bundled games is 164, and the total value of my non-bundled games is 220. So my total CV should be 220x1.2, while according to the website, it's even lower than my non-bundled games alone! O.o

EDIT: As mentioned in comments below, I did include my latest Bioshock giveaway in the count by mistake, so the count (as made today) comes up right. I still wonder why I was up to 260$ before, though, and it just now dropped to 215$.