Congratulations, that is truly good news
The point I'm trying to make is that how far off you are from your goal has nothing to do with your success rate- it's whether or not your writing was originally marked incorrectly, which in your case is clearly what happened.
The other side of this coin is the vast number of others who were also in need of a half band and didn't get it- they far, far outnumber you, unfortunately.
Let's think of it this way- if you saw a guy coming out of a casino with a big bag of free money, would you conclude that the casino was a great place to invest your hard-earned money? I'm pretty sure that you wouldn't, because such an idea is ridiculous.
The IELTS remark scam is much the same. Actually, your odds are probably better at the casino, lol.