Korea, Japan, and China all use both inches and centimeters, but mainly the metric system. For example, the total length of the scissors is expressed in inches in all 3 countries. However, centimeters and millimeters are used for the parts and precision manufacturing processes.
A digital caliper with both units is helpful, which would measure more accurately and efficiently when you have to replace a bolt or purchase the parts for repair.
Scissor factories usually use standard-sized bolts, but it is not unusual to design a customized size bolt.
0.01mm is a minimal difference; slight errors might occur even when measuring the same part multiple times. The following pictures show you how to measure the length and diameter.
The following pictures show you how to measure the square hole circled by the red line. As you see in this photo, the actual size is 4.08mm. The standard size is 4.0mm, but the factory made it 0.08mm bigger. The standard size for this square part of the bolt is 4.0mm, but its actual size is 3.95mm.
In general, the square holes are made bigger, and bolts are made smaller than their standard size to make them fit together easily.
This time, let's check the size of the circular hole inside the blade. The standard size is 5.0mm, but the actual size is 5.01mm. The round part under the bolt head is 4.92mm, but it is for a 5.0mm hole.
Let's measure the circular hole outside of the blade. It is 7.09mm, and the head of the bolt is 6.99mm. The standard size for the hole and the bolt is 7.0mm.