equivalent-mutant.diff

public function calculateExpectedValueAt(DateTimeInterface $date)
{
    $diffInDays = (int) $this->startedAt->diff($date)->format('%a');

    $multiplier = $this->initialValue < $this->targetValue ? 1 : -1;
    $initialAveragePerDay = $this->calculateInitialAveragePerDay();

-    return $this->initialValue + ($initialAveragePerDay * $diffInDays * $multiplier);
+    return $this->initialValue + ($initialAveragePerDay * $diffInDays / $multiplier);
}