Yes, it's 100% a cultural thing: I went to schools in the UK where punishment was regularly practiced by the schoolmasters and mistresses (yes, that is what they were actually called and what we had to refer to them as). The standard unit of punishment was "six of the best".

Prior to the 1970s, the UK used all sorts of measurement schemes for money and weights that were non-decimal i.e. until 1971 the UK did not use a currency that divided into 100 subunits e.g. 100 cents in a dollar. Instead a pound was subdivided into 20 shillings, each of 12 (old) pence - there's that number. You can read more about this bizarreness here: https://en.wikipedia.org/wiki/Decimal_Day

Personally, I like both approaches, i.e. being given a number in advance or a Mistress letting loose until she's satisfied. I was once owned by a mistress who took both approaches: She would start off by just letting loose and start a long, heavy, cold caning with no indication of when the end would come. Then she would announce that next would be becoming my last 10, and I would have to count them. I would count them diligently and thank her for each one; however, without fail, when the count reached eight, she would correct me and tell me that the correct count was actually seven. I would apologize and adjust my count to seven, and then the count would move to eight again, and she would correct me and reset me back to seven and keep correcting me back to seven until she had probably corrected me more times than the original 10. The wildest part of it for me was my complete acceptance of her absolute right to define my reality this way.