• 1.6 baseline — 0.6 × season 1.8 (16 gm) + 0.4 × last 10 1.4
• −0.1 opponent leak — they concede 33.9/game vs a 35.7 league average
• +1.1 at this ground — averages 2.7 there (59 gm)
• +1.3 wet forecast — averages 2.9 in the wet (15 gm)
• vs them: averages 2.2 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.