• 4.5 baseline — 0.6 × season 4.3 (16 gm) + 0.4 × last 10 4.9
• +0.2 opponent leak — they concede 195.2/game vs a 185.9 league average
• −0.2 at this ground — averages 4.3 there (26 gm)
• vs them: averages 10.3 over 3 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.