What interests me is that when you take off
x seconds - you're
on average really taking off
x.49 (9 repeating) seconds.
Here's my justification, for certain clocks:
When the display changes from 8:00 to 7:59 immediately at the beginning of a quarter, and not a second after the clock is started, there is really 7:59.99, .98, .97, .96, you get the idea remaining in the quarter. The upper limit is 7:59.9 (9 repeating). The lower limit is 7:59.0 exactly.
That difference is almost 1 full second. If the clock says 3:45 and you have to remove 6 seconds, then you are changing the clock to read 3:39 - which I'm certain the clock interprets as 3:39.0. If the clock memory is 3:45.98, then the resetting loses .98 seconds.
If you think that .98 seconds isn't much, ask Christian Laettner, Michael Jordan, or even the 1972 US Olympic team.
Edit:
I will propose a second auxiliary button on a scoreclock: Adjust. User presses Adjust, then 1 to remove seconds (or 3 to add), then the number of seconds to adjust the clock by.
My first additional button is called Factor. It works like this: you press Factor, then two digits such as 85, then Factor again. This tells the clock to remove a second from the display (and internal memory) every 0.85 seconds. Used in a blowout only, you can save 288s, or 4min 48s!!