• 12.5 baseline — 0.6 × season 13.3 (16 gm) + 0.4 × last 10 11.4
• +0.5 opponent leak — they concede 193.8/game vs a 186.3 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• vs them: averages 14.3 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.