• 1.4 baseline — 0.6 × season 1.3 (12 gm) + 0.4 × last 10 1.4
• −0.0 opponent leak — they concede 12.4/game vs a 12.8 league average
• +0.8 at this ground — averages 2.2 there (68 gm)
• vs them: averages 1.9 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.