The Specifications Of The Sewing Thread

Sewing thread specifications 202\203\202\303402\502\403\602\604\602\209, 202604 of them are the same product (basically the same thickness), 203 and 206 is also the same product (basically the same thickness), the standard name? As 402 standard is 40 s / 2, 604 standard is 20 s / 2, etc.