• 4.4 baseline — 0.6 × season 4.4 (9 gm) + 0.4 × last 10 4.4
• −0.3 opponent leak — they concede 87/game vs a 93.4 league average
• +2.4 at this ground — averages 6.8 there (12 gm)
• +1.3 wet forecast — averages 5.8 in the wet (4 gm)
• vs them: averages 6.6 over 8 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.