Which example demonstrates the correct writing format for numbers?

The choice showcasing the correct writing format for numbers is the one indicating that the gap must not exceed 2 mm. This example adheres to guidelines for writing numbers in technical and scientific contexts, where specific measurements are commonly presented in numerals. Using numerals for measurements helps convey clarity and precision, essential in professional and academic communication.

In this context, numeric representation is more effective than writing out the numbers as words, especially for measurements, as it aligns with the conventions often found in technical documentation. Standards vary depending on the context of the writing, but when specifying exact values, especially in scientific and technical writing, numerals are generally preferred.

While other options may be contextually acceptable in different scenarios, they don't consistently align with established guidelines for number representation in formal writing. For instance, monetary values might be presented differently in more casual writing, while writing out small numbers as words can be acceptable in less formal contexts, but precision and clarity take precedence in professional communication. This makes the second option the most suitable in this case.