Bad at Rounding and Writing

Tuesday, October 8th, 2019

After posting yet another tale of my Apple Dumbwatch on October 7th, I heard from several readers who correctly guessed that my screenshot might be from earlier in the month. In fact, I’d actually taken it on October 4th. Given that, it appeared that the Activity app might actually be doing live or live-ish updates to the required per-day average. Did that explain the seemingly bad math? It turns out the answer is yes, but it also exposes several other issues. Let’s have a look.

First, I looked back at a screenshot from earlier in the day on October 4th. This was snapped at 4:02 PM:

Challenge stating 'Earn this award with 2560 Exercise minutes - that's about 79 minutes a day'.

As you can see, this says “about 79”. I had 2,236 minutes left to obtain, and 28 days (counting the 4th) remaining. How does that math check out?

2,236 minutes remaining/28 days remaining = 79.86 minutes/day

Now, 79.86 minutes per day is sort of close to “about 79”, but it really ought to be “about 80”. Also, remember that at 4 PM, the 4th is already 2/3 over.

My original image was from 10:37 PM of that same day, October 4th. Here it is again:

Challenge stating 'Earn this award with 2560 Exercise minutes - that's about 79 minutes a day'.

As you can see, I’d done some more Exercise minutes since 4 PM. I now had 2,214 minutes left to obtain, and 28 days (again, counting the 4th) remaining. The math on this actually works out to just over 79 minutes:

2,214 minutes remaining/28 days remaining = 79.07 minutes/day

That certainly is close to 79, though again, if you do 79 minutes a day, you’ll come up short. Worse, at this point the 4th was nearly over, yet it was still being counted in the averaging. That seems like a problem.

Finally, I did a check on the 7th, at 11 AM. Here, you can see that the estimate has gone up, as I’ve fallen slightly off the pace:

Challenge stating 'Earn this award with 2560 Exercise minutes - that's about 79 minutes a day'.

One more time, let’s check that math.

2,107 minutes remaining/25 days remaining = 84.28 minutes/day

As before, this is close enough to “about 84” for Apple’s purposes, at least. Clearly, Activity is doing live tracking as the month progresses, rather than just doing one calculation (2560 minutes /31 days = 82.58 minutes/day)). That’s a nice idea, but there are several obvious problems here. Specifically:

  • The current text fails to indicate that the estimate provided is for the remainder of the month. Something like this could be an improvement:

    “Get 2560 Exercise minutes this month to earn this award. You’ve earned 453 minutes so far, so you just have 2,107 left to go. That’s about 84 Exercise minutes a day, for the rest of the month.”

    That would make it much more obvious that this estimate is for the rest of the month.

  • Activity is counting the current day in its averaging, no matter when in the day you are. Surely at 10:37 PM, or worse, 11:59 PM, the current day should not be counted fully in the averaging.

  • Finally, anything over X minutes should be rounded up to X+1 minutes, to avoid ever coming up short. So, 79.8, and even 79.1, should become “about 80”.

It seems I was incorrect in maligning the Apple Watch’s math skills. However, its rounding skills could definitely do with some improvement, as well as its copyediting.


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