The lifeclock is alterable, as we see when the Übercomputer sets Logan’s lifeclock to blinking red years before he is actually due to Carousel. This procedure must be beyond the capabilities of the populace since it could be used to blackmail citizens, or, if reversible, to allow them to delay carousel.
Why this procedure was designed in a way to cause stress and discomfort on the part of the subject is unclear. Since the computer is counting on Logan and needs his cooperation, it should have taken the exact opposite approach. Even if the discomfort is a necessary part of the retrogram, the computer should have handled it like a friendly nurse, explaining that there will be some unavoidable pain, and given Logan some tools to manage it like a number to count to. And c’mon, it should skip the ominous red light.
The other design consideration is the placement of the divot in which Logan must place his lifeclock for retrogramming. All told, it’s pretty good. It’s a natural placement, almost difficult for Logan to avoid putting his hand in the right spot. Even if the Übercomputer is going to just “sneak up” on Logan and retrogram him without warning, it’s the right spot given that the Übercomputer seems to have no complex actuators.
There’s an interesting issue about the divot that depends on the level of pain that Logan is feeling. If it’s too great, Logan might jerk his hand away and ruin the retrogram. In that case, the arm of the chair should hold Logan’s hand in place, like one of those automated blood pressure cuffs. But the pain we see on Logan’s face in the scene doesn’t look that great. It looks like just enough to force him to concentrate to keep it there, to do his duty and comply. In this case even if the pain isn’t a necessary part of the operation, the Übercomputer might want to add that pain in, just as a test of his continued compliance.