Expected. Detected. Gap.
Expected: establish the baseline. Identify the source, instrument, relationship and effective date. A baseline is a reference for comparison, not a guarantee that one source answers every question.
Detected: inspect the observation. Record what was observed, where it came from and when it was captured. A source's statement and its underlying accuracy are not the same thing.
Gap: explain the comparison. Describe the difference, its possible explanations and the evidence needed to resolve it. Where the information is insufficient or not comparable, say so.