When making a measurement, one must give consideration to the degree of precision to which one knows the measured quantity. The markings on the instrument provide a  level of certainty to the measurement. But every measurement must also account for an estimated digit that demonstrates how far between the markings that the measured amount is.
 

Making a measurement - a proper one - may be more difficult than you think. Don't worry - we can help. The graphic below should provide considerable help. The trick to a good measurement is providing an estimated digit. You can read about this below and see the three caterpillar examples that are given. But don't get squeamish because significant digits do not need to frighten you. Take your time. Use the markings on the device to determine the range the measured value falls into, and then provide an estimated digit that indicates where within the range the measurement is. You got this!