• 1.2 baseline — 0.6 × season 1.4 (19 gm) + 0.4 × last 10 0.9
• −0.1 opponent leak — they concede 53.8/game vs a 56.6 league average
• +0.6 at this ground — averages 1.8 there (78 gm)
• vs them: averages 2.6 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 9: 5 — far outside his usual range; kept in the average, not smoothed away.