• 1.4 baseline — 0.6 × season 1.3 (9 gm) + 0.4 × last 10 1.5
• +0.2 opponent leak — they concede 14.7/game vs a 12.8 league average
• +1.7 at this ground — averages 3.1 there (31 gm)
• vs them: averages 3.4 over 5 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.