• 7.0 baseline — 0.6 × season 7.3 (20 gm) + 0.4 × last 10 6.5
• −0.5 opponent leak — they concede 87/game vs a 93.4 league average
• −1.1 at this ground — averages 5.9 there (17 gm)
• −2.2 wet forecast — averages 4.8 in the wet (5 gm)
• vs them: averages 4.6 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.