• 4.7 baseline — 0.6 × season 4.7 (19 gm) + 0.4 × last 10 4.7
• +0.3 opponent leak — they concede 164/game vs a 155.4 league average
• +0.1 at this ground — averages 4.8 there (32 gm)
• vs them: averages 4.3 over 4 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.