• 3.4 baseline — 0.6 × season 3.3 (6 gm) + 0.4 × last 10 3.6
• +0.4 opponent leak — they concede 104/game vs a 93.4 league average
• +1.1 at this ground — averages 4.5 there (10 gm)
• vs them: averages 4.0 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.