What Significant figures are read directly from the measuring instrument plus one more digit?

Significant figures are the digits in a measurement that contribute to its precision, including all the digits that are known with certainty plus one estimated digit. For example, if a ruler measures a length as 5.6 cm, the "5" and "6" are certain figures, while the implied uncertainty in the last digit makes it significant as well. This practice helps convey the accuracy of the measurement and ensures clarity in scientific communication. Thus, when reporting measurements, it's essential to include all significant figures to reflect their reliability.