I think a lot of it is due to you simply not registering the other numbers you see. For example, you see 1:23 2 days in a row, and that's pure coincidence but you note it in your head. Then, the next week, whenever you see that time, you think "wow, 1:23 again" yet you don't realize that you checked the time like hundreds of times prior, but since those other numbers didn't appear, you didn't register it in your head. So from now on, whenever you see 1:23, you think that's your super special time
Aside from that, you can manufacture any number you want, and that was demonstrated in the movie "23". I found it to be rather silly. I weigh 194 lbs. 19 + 4 = 23! I'm 32 years old...that's 23 backwards. I was born at 9:59am 9 + 5 + 9 = 23!! OMG, it's a sign from above!!