• 1.7 baseline — 0.6 × season 1.7 (16 gm) + 0.4 × last 10 1.8
• +0.3 opponent leak — they concede 14.7/game vs a 12.8 league average
• −0.7 at this ground — averages 1 there (6 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.