• 12.1 baseline — 0.6 × season 11.8 (18 gm) + 0.4 × last 10 12.6
• +0.0 opponent leak — they concede 213.7/game vs a 213.6 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• vs them: averages 9.7 over 9 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission. Round 20: 19 — far outside his usual range; kept in the average, not smoothed away.