The least count of the measuring instrument represents the smallest reliable measurement it can make.

• Least count = $1\text{ mm}=0.1\text{ cm}$.
• The maximum absolute error (uncertainty) in a single measurement is generally taken as half of the least count (or sometimes the full least count depending on convention, but in physics problems, half the LC is standard for identifying discrete scale intervals).
• Uncertainty = $\pm 0.1\text{ cm}/2=\pm 0.05\text{ cm}$.