• 1.3 baseline — 0.6 × season 1.4 (17 gm) + 0.4 × last 10 1.2
• −0.1 opponent leak — they concede 22.6/game vs a 23.6 league average
• +0.7 at this ground — averages 2 there (31 gm)
• +0.7 wet forecast — averages 2 in the wet (11 gm)
• vs them: averages 1.6 over 5 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.