• 3.2 baseline — 0.6 × season 3.4 (18 gm) + 0.4 × last 10 2.8
• −0.2 opponent leak — they concede 53.9/game vs a 56.6 league average
• −0.7 at this ground — averages 2.5 there (8 gm)
• vs them: averages 2.0 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.