• 11.6 baseline — 0.6 × season 12.1 (16 gm) + 0.4 × last 10 10.9
• −0.3 opponent leak — they concede 181.3/game vs a 185.9 league average
• +3.8 at this ground — averages 15.4 there (54 gm)
• vs them: averages 15.1 over 13 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 3: 22 — far outside his usual range; kept in the average, not smoothed away.