• 2.3 baseline — 0.6 × season 2.6 (16 gm) + 0.4 × last 10 1.8
• −0.1 opponent leak — they concede 333.3/game vs a 344.7 league average
• +0.1 at this ground — averages 2.4 there (17 gm)
• +0.9 wet forecast — averages 3.2 in the wet (5 gm)
• vs them: averages 5.0 over 1 game — 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.