• 30.2 baseline — 0.6 × season 29.8 (6 gm) + 0.4 × last 8 30.8
• +2.7 opponent leak — they concede 1838.8/game vs a 1687.8 league average
• at this ground: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 50.0 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.