• 2.7 baseline — 0.6 × season 2.7 (16 gm) + 0.4 × last 10 2.8
• +0.7 opponent leak — they concede 117.8/game vs a 93.4 league average
• +1.3 at this ground — averages 4 there (59 gm)
• +0.8 wet forecast — averages 3.5 in the wet (15 gm)
• vs them: averages 3.8 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.