ike 7:12. She explained that if you put down a round number, people assume it's approximate, so you can come 20 minutes later without a problem. The odd numbers stick out in their minds, though, and then some come to see will it actually happen at exactly twelve minutes past the hour.
In our minds certain times are round times, on the hour, on the half hour, and even on the quarter hour. But we don't consider a time ending in 12 to be a time to set an event. That's why it comes across as very specific.
In TaNaCh we see that kind of use of numbers, as well. I've been meaning to address the subject ever since I came across the absolutely wrong assertion that Joel M. Hoffman makes in And God Said (pp. 87-88). Falling into the logical fallacy of begging the question, he asserts that as 12 is a round number in Biblical usage, when it says that Seth (that is Adam's third son through whom the line continues) lived to 912 years, it does not mean it literally but as an approximation.
Hoffman is forced to take this position because he doesn't believe that the lifespans of hundreds of years could possibly be literal. Conseuqently, he presents 912 into a round number that could stand for something like 1000 to just meant a long time. That makes absolutely no sense in context, for Seth followed Adam who lived 930 years and was the father of Enosh who lived 905 years. Seth's grandson, Kenon lived for 910 years. It doesn't make sense to use 912 as a round number and then to distinguish it from 905 and 912.
Just to demonstrate that I'm not misrepresenting Hoffman's take, I'll quote exactly what he says on pp. 87-88: "Notice the '12' at the end. That was a round number in antiquity. Whether Seth was really that age or not, readers of ancient Hebrew would see such a number as a round number, while we do not. Genesis 14:4 talks about 'twelve years' of service. Should the translation make it 'ten'?"
No, because the Bible actually uses ten as a round number in contradistinction to twelve, which is used as a specific number. Hoffman's error here is to mistake a number seen a frame of reference as approximate. Twelve is a very significant number in Jewish thought, as the nation is made up of twelve tribes that correspoind to the twelve months. But that does not make it a unit that can be used as a genral number to mean a fairly large amount the way ten is used at times -- not just in modern usage but in TaNaCh.
I was reminded of this in rereading Ruth this year. We see exactly the contrast between significant, specific numbers and round numbers. At the beginning of the story, we are told about Elimelech's family that moved out of their homeland to the fields of Moav and remained there "ke'eser shanim" that is like 10 years, indicating 10 can be used as an approximation, much like we may use decade for exactly 10, just under 10 or even 10 1/2 years.
At the end of the story, Naomi is told by her neighbors that Ruth has proved better to her than seven sons. Like the number 10, the number seven is frequently used in a non-literal sense. Though it may not be used as a round number today, seven -- not twelve -- certainly is usedi n that way in TaNaCh. The neighbors don't mean Ruth is better than seven but not eight or that she is more than twice as good as three sons. It's not a literal count but an approximation.
In that way, seven contrasts with six, which is a significant specific number. That's the number of measures of barley that Boaz gives Ruth when she leaves the granary with his assurance that he will take care of the question of marriage and redemption. It is because six is such a specific number that Chazal feel a need to explain the significance of that gift. Six, like 12, has to mean something in particular, while seven and ten can be approximations.