• 4.9 baseline — 0.6 × season 5.6 (21 gm) + 0.4 × last 10 4.0
• +0.2 opponent leak — they concede 192.6/game vs a 185.9 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• vs them: averages 9.0 over 5 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.