I count really strange things obsessively.
Like words - I'll see a street sign, say it is "Thompson St". Each letter is 1 value, but then the area in the middle of the o's and p count as 1 as well. So that's worth 12. I count peoples faces as well; a face is worth 15. Each eye is 3 (black bit, coloured bit, white bit), nostrils are 1 each, nose is 1, and mouth is 6 - each lip is one, tongue is 1, area under tongue is 1, teeth are 1, and gums are 1. I think it's the different colours that I'm counting.
I'll sometimes look harder to reduce or increase the number to make it an even number or a multiple of 5 because its neater.
Also not surprisingly, my car air conditioner is always on 18, 20 (my favourite coz it's even AND a multiple of 5), 22 or 24. I can't stand looking at it and seeing it on 23, even though its usually the most comfortable temperature. Same goes with TV / radio volume.