• 36.0 baseline — 0.6 × season 38.8 (17 gm) + 0.4 × last 10 31.9
• +0.9 opponent leak — they concede 558/game vs a 544.2 league average
• +2.0 at this ground — averages 38 there (18 gm)
• +5.6 wet forecast — averages 41.7 in the wet (6 gm)
• vs them: averages 29.5 over 2 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.