• 11.3 baseline — 0.6 × season 11.3 (8 gm) + 0.4 × last 8 11.3
• +0.5 opponent leak — they concede 386.5/game vs a 369 league average
• at this ground: too thin to count (2 gm) — shown, adds nothing
• vs them: averages 15.0 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.