Confusing Corporate Governance: Can Someone Explain 'Materiality' in Share Price?

Mainly because textbooks never give a concrete example, I'm stuck on 'materiality' in company law. They just say it's when a change affects a company's share price or operations significantly. But how significant is significant? For example, a company announces a profit of 100 crores in a quarterly report. Later, it's revealed that the profits were 20 crores, but just included some one-time sales. Is that material or immaterial? How do courts decide? Can someone give a real-life example of a case where 'materiality' was a crucial issue?