There isn't much butter left in the refrigerator.

Literal

Refrigerator [in-には] butter [topic-は] not-much is-not-remaining.

あまり~ない ('not much, not very') is a quantifier negation pattern, sitting between ありません ('none at all') and ほとんどない ('hardly any') in degree. 残っていない is the resulting-state negative of 残る (not in the state of remaining = not left).