• 4.9 baseline — 0.6 × season 4.9 (10 gm) + 0.4 × last 10 4.9
• +0.2 opponent leak — they concede 195.2/game vs a 186.3 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• vs them: averages 5.0 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.