Mostly, I turn it down to the point where setting it any lower will degrade my listening experience. I seldom look at the numbers at all - it can be different for different channels and different types of programmes anyway.
Mine has 16 levels, which means that I like multiples of four - unfortunately, the most comfortable setting is 9. Drives me nuts.
Multiples of 5 is necessary or else someone will get hurt.
Maybe that’s why I don’t watch TV that much.
In all things numerical (tv volume, microwaves, gas pumps, etc.) I have always prefered numbers that end in 7 or 9.
Not necessarily volume, but when I have to pick a random number (such as how many rows to crotchet in a scarf), I like odd numbers. Except for 5, that’s too regular and so my brain classifies it as even. I think I may be the world’s only OCD person who can’t stand it when things are too orderly.
ETA: my favorite numbers are 3, 7, and 9, so I try to go for numbers that end in them. But I don’t like to put them together, because I’m a synesthete and the colors clash horribly.
(sorry) Mine goes to 11.
Oh balls, I came in to say that.
I don’t have volume control OCD, but whenever I set my alarm it’s got to be at a 5-minute time (7:30 or even 7:35 but never 7:33). And if I ignore it and snooze, I can’t get out of bed unless it’s another 5-minute mark. So it’s 8:05, shall I get up? Shall I, shan’t I, can I afford to lie in a bit longer… aaaaaaand now it’s 8:06. Damn! Have to wait another four minutes!
Yep, I do multiples of 5. I’m usually between 15 and 35. 15 or 20 for Playstation3, it seems to put out loud audio. 25 or 30 for normal TV viewing, sometimes 35 if a show is particularly quiet. 35 for movies as well, the dialog is often too quiet but the sound effects are too damn load.
Those are my exact two rules. Same thing with the volume on the car stereo/CD player. Oh, for a dial you can just turn with no numbers attached!
ETA: I remember how my grandma and my father are both anal (he got it from her) but in slightly different ways so they drove each other nuts. I picked up some of it, as above, and expect to be no worse than my father. Imagine my discomfort when he turned the volume to 17 and left it there. 