• 15.5 baseline — 0.6 × season 15.0 (4 gm) + 0.4 × last 10 16.3
• +1.0 opponent leak — they concede 368.1/game vs a 344.9 league average
• at this ground: too thin to count (1 gm) — shown, adds nothing
• vs them: averages 26.7 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.