Bob, that all seems a bit too technical for my brain to digest for the minute.Oz But thank you anyway. Very interesting.
Think of a car odometer. It used to be that most cars had odometers that only went up to 99,999 miles. When a car got to 100,000 miles, the odometer rolled back to zero and started over. It is not uncommon for a car to last well past 100,000 miles, so past that point, it used to be the case that the odometer no longer reflected the true mileage. My first car, a 1969 Falcon station wagon, lasted for about 220,000 miles. At some point, I stuck a “1” sticker next to the odometer to make it show the correct mileage, and on a trip where I knew it was going to roll over again, I brought along a “2” sticker, and me and my passengers were all watching for it to happen, whereupon we pulled over, and with great pomp and ceremony, I removed the “1 ”sticker” and put the “2” sticker in it's place.
Most modern cars now have odometers that got up to 999,999 miles, so they won't roll over unless a car reaches 1,000,000 miles, which very few ever do.
I'm assuming that a DSLR stores its shutter count as an unsigned binary integer; and how big a number it can store depends on how many bits it uses. When it passes that number, it will roll back to zero, just like an old car's odometer. I'm thinking it's possible that some older DSLRs might use only a 16-bit number, which would roll back to zero at 2[sup]16[/sup], which would be 65,536, a limit that many DSLRs might plausibly exceed. Thus, the D700 that you think only has 896 clicks on it might really have 65,536+896=66,432 clicks.