• 4.8 baseline — 0.6 × season 4.8 (10 gm) + 0.4 × last 10 4.8
• +0.1 opponent leak — they concede 158.8/game vs a 155.4 league average
• −0.2 at this ground — averages 4.6 there (8 gm)
• vs them: averages 3.0 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.