• 3.3 baseline — 0.6 × season 3.4 (18 gm) + 0.4 × last 10 3.2
• +0.2 opponent leak — they concede 38/game vs a 35.7 league average
• −0.7 at this ground — averages 2.6 there (16 gm)
• −1.3 wet forecast — averages 2 in the wet (8 gm)
• vs them: averages 1.1 over 9 games — 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.