• 3.2 baseline — 0.6 × season 3.4 (13 gm) + 0.4 × last 10 2.9
• +0.2 opponent leak — they concede 60.6/game vs a 56.6 league average
• +0.1 at this ground — averages 3.3 there (7 gm)
• 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.