Modifies abstract nouns — 损失 (losses), 影响 (influence), 价值 (value), 贡献 (contribution), 潜力 (potential). Can be positive (huge value) or negative (huge damage), depending on what it describes.
grammar
Structure: 不可 (cannot) + 估量 (estimate). The 不可 + verb pattern produces many similar idioms: 不可思议 (unthinkable), 不可救药 (incurable), 不可一世 (arrogant beyond measure).
