• 29.0 baseline — 0.6 × season 28.6 (18 gm) + 0.4 × last 10 29.6
• −2.9 opponent leak — they concede 1519.7/game vs a 1686.6 league average
• at this ground: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 22.3 over 10 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.