• 5.2 baseline — 0.6 × season 5.6 (7 gm) + 0.4 × last 10 4.7
• +0.9 opponent leak — they concede 108.9/game vs a 93.4 league average
• −1.2 at this ground — averages 4 there (9 gm)
• vs them: averages 4.0 over 1 game — 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.