# C1215 — Explain the exact cancellation in the Rounded head difference

## Question

Why do local rounding changes preserve the total430?

## Inputs

```json
{}
```

## Sources

```json
[
  "C1214"
]
```

## Opened utc

2026-09-28T05:29:10.374185+00:00

## Results

```json
{
  "cancellation": {
    "path": "model/whole_genealogy_rounded_head_cancellation.json",
    "sha256": "3d45a7d600eda8d3b759b2b612bd9ca5267b4804fb9b58fa83e23698e46fce33",
    "bytes": 436
  },
  "located_errors": [
    {
      "name": "Lamech",
      "difference_error": 4
    },
    {
      "name": "Arphaxad",
      "difference_error": -2
    },
    {
      "name": "Shelah",
      "difference_error": -2
    }
  ]
}
```

## Finding

The Rounded Cumulative total remains430 because Lamech contributes+4 and Arphaxad/Shelah contribute−2 each. The cancellation explains the shared head while predicting an internal displacement field.

## Reassessment

Reconstruct the internal rounding-displacement field rather than stop at its zero total.

## Checks

```json
{
  "cancels": true,
  "heads430": true
}
```

## Closed utc

2026-09-28T05:29:10.374656+00:00

## Record provenance

Exact record hash: `268065dc94c7df85f65656030e021aa590c9aa49622bcf48c4a9fb9d73239916`

Source journal: `Research_Cycles/C1132_C1431_Recovered/journal.json`