Below is a guide on what the scores I've given mean to me personally so that you have some context of what's what. Similar scoring criteria can be assumed for any manga scores too.
10 = Leader of its genre, next to zero faults and appealed to me on a personal basis. Must also have a good opening, a character I can get very attached to as well as a solid and well explained plot. That plot could be a thriller or a simple slice of life narrative. As long as its developed and interesting, it's eligible for a 10.
9 = It's going to stick in my mind for a long time and become a case study for me to compare to when explaining how good or bad a show is. It's missing something on the 10 list criteria but it's still one of my favourite shows to date.
8 = It was missing that certain something that would have placed it into my list's elite but it was very good nonetheless. This tends to be shows where I thoughts they were certainly above 'decent' or 'good' but not to the extent where I'd recognise them as 'great' or 'remarkable'.
7 = Basically this is my 'I enjoyed it somewhat but I don't plan to ever re-watch it' category. I'm pleased I spent my time on said show but it's unlikely to become anything more than just another show on my list. Not a personal favourite or anything special, just kind of there.
6 = Forgettable but satisfactory on a core level. Short series (around 12 episodes) can score this and still be okay but longer series (24+) haven't done well with this scoring. Then again if it's that long and it's only on track for a 6 I'll probably have dropped it anyway. A lot of shows that I felt just weren't for me will be around here.
5 = Similar to a 6 but in this case the show notably bored me. It wasn't even necessarily bad but on a personal level it failed to be a source of entertainment. This is when I start regretting any kind of time input into said show.
4 = The lowest I'll likely ever finish a show at and this is usually only if it's a 5/6 and has a terrible ending but I'm so close to the end I don't value dropping it. It's at this point the words 'bad' and 'tiresome' come to mind.
3 = Shows that literally make me more depressed or fed up than when I started watching them. Doubtful I'll finish anything here or lower unless it's a co-op watch with a friend or because I just happen to hate myself on said day.
2 = Shockingly bad to the point where they not only bored me, but also damn right annoyed me. Be it creative decisions no one could justify, animation or art that looks like they drew it whilst high or a plot which bewilders even the imagination of mankind. These are the shows I will criticise till the end of time.
1 = I had never expected to give a 1. I swore it would require something beyond the most corrupt and terrible minds to even approach this rating. Then I saw Ari Ningen Monogatari.