Please note: This is the way I see things here on Mechanics. Bob and Ducati may have a slightly different view. I'll leave it up to them, if they feel differently. I really don't believe they would, but I don't want to pretend to speak for them.
I've only been a mod on here for a short while, so can only comment upon what has happened during the time since I've been a moderator. To that end, since you brought up numbers, I'm finding myself free to talk about your numbers. Specifically about flags, you've produced 15 flags over the past month or so, three of which have been declined. Those three were marked as: obsolete; too chatty; spam. The obsolete one is the one you have listed in your question. With it I'll say, it may or may not have deserved to be deleted. Not sure on the second one. The third one marked as spam was definitely not spam (and I can attest to this as I'm the one who declined it and left you a message as to why).
I've read through your question on Meta and to Catija's answer which you selected as the answer. While this may be the general guidelines on SE overall, I'll remind you it is still up to the opinion of the moderator handling your flag as to how to handle it. Catija cannot come on this stack and make the call. Only myself, Bob Cross, and DucatiKiller have those privileges (along with the Community Moderators who can, if they choose, but usually don't if there's no issues). I cannot come onto the stack which you moderate and do this either. If I flag something on Graphic Design and you moderate the flag, you decide whether the flag is worthy and handle it accordingly. This is the whole reason why we have human moderators and not bots which do the bidding of each person who flags something.
For the most part, all I can say is, while we (the mods) try to do our best, we are still human and imperfect. Who knows why exactly any of these three were declined, but they were. (Well, I gave you one which was explained, but only because I distinctly remember it.) Please don't take it personally as to why one of your flags was declined. Each of us have to make a judgment call and we do. We were elected to make those judgement calls and we fulfill that duty.
I'm not sure what else I can say about the matter. I hope this helps you understand.
Oh, I did notice, you had one flag which was disputed ... IIRC, that's not a mod thing, but an OP who can dispute it. So, that's probably the fourth one you're talking about.
Now that I know your reasoning for asking this question in the first place (worried about an autoban on flagging), please read through this answer on Meta which spells out how the autoban works and the thresholds at which they are imposed. Believe me when I say, you are nowhere near this threshold! :o)