• 2.3 baseline — 0.6 × season 2.3 (12 gm) + 0.4 × last 10 2.3
• −0.3 opponent leak — they concede 80.8/game vs a 93.4 league average
• +1.5 at this ground — averages 3.8 there (9 gm)
• +1.5 wet forecast — averages 3.8 in the wet (12 gm)
• vs them: averages 4.5 over 6 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.