When starting to record the original data, we should carefully estimate any data with computational significance and correctly record the significant figures of the magnitude. The minimum dividing value of a 50 ml burette is 0. 1 ml, and because an estimated number is allowed, two decimal places can be recorded, such as 12.34 ml. If only 12.3 ml is recorded in the original record, it means that a relative error of 1.6% may occur. Because the original records are unreasonable, the accuracy of the data has dropped by an order of magnitude.

The measurement result of any specific quantity is the measurement value obtained through measurement, also called order of magnitude. The magnitude is usually expressed by multiplying a number by the unit of measurement. Because the perfect measurement process cannot be realized artificially, the measurement results inevitably contain errors. In order to show the accuracy of the measurement results, the digital part of the measurement results of a specific quantity is represented by significant figures.

The dimensions indicating the test results and their effective figures shall be filled in as specified in this analysis method. Only the last digit in a data is allowed to be an estimated (suspicious) value, and all other digits are valid (credible), thus determining the digits of integers and decimals.

A valid number consists of one or more "reliable numbers" and one "last inaccurate number". The significant digit of the significant digit is the sum of the "reliable digit" and "the last digit is inaccurate". Because the "last inaccurate figure" has different degrees of inaccuracy under different specific measurement conditions, in principle, this standard does not stipulate the interval of revision.