Two screen sessions can look identical from the outside. Both may involve the same app, the same chair, and the same number of minutes. The difference is the path that led to the session.
When screen time follows an offline action, the session carries evidence of prior agency. The user did something measurable before consuming attention. That sequence changes the psychology of the reward.
The ledger is important because memory is unreliable. Without a record, a user may remember the guilt of the scroll more clearly than the useful action that came before it.
A visible credit system makes the exchange explicit: the real world came first, the screen came second, and the balance remains available for inspection.