• 4.7 baseline — 0.6 × season 4.9 (9 gm) + 0.4 × last 10 4.5
• −0.4 opponent leak — they concede 141.4/game vs a 155.4 league average
• at this ground: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 2.0 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.