• 4.1 baseline — 0.6 × season 3.8 (13 gm) + 0.4 × last 10 4.5
• −0.1 opponent leak — they concede 55.5/game vs a 56.6 league average
• at this ground: too thin to count (3 gm) — shown, adds nothing
• vs them: averages 3.0 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.