• 2.8 baseline — 0.6 × season 2.9 (16 gm) + 0.4 × last 10 2.6
• −0.1 opponent leak — they concede 152.3/game vs a 155.4 league average
• +0.5 at this ground — averages 3.2 there (36 gm)
• vs them: averages 3.0 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. Round 4: 6 — far outside his usual range; kept in the average, not smoothed away.