• 4.6 baseline — 0.6 × season 5.2 (20 gm) + 0.4 × last 10 3.7
• +0.0 opponent leak — they concede 94/game vs a 93.4 league average
• −0.6 at this ground — averages 4 there (10 gm)
• vs them: averages 4.8 over 11 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.