• 17.7 baseline — 0.6 × season 17.7 (10 gm) + 0.4 × last 10 17.7
• +1.6 opponent leak — they concede 594.5/game vs a 544.6 league average
• +10.9 at this ground — averages 28.6 there (10 gm)
• vs them: averages 33.3 over 8 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: 44 — far outside his usual range; kept in the average, not smoothed away.