I just visited an official github page of TC39 and noticed that some of the names end with numbers, for example:
Where do these numbers come from? Why not TC47, ecma-777?
Before reading the comments under this question I though that ECMA international was an organization that was responsible only for ECMAScript and nothing else. And all these numbers in this context were strange for me. But now, I understand that ECMA is an organization that standardizes things. And ECMAscript (alias for the ecma-262 specification) is one of those things.
Answering my question 262 means the next available number within ECMA organization to reference the specification, as well as -402. And 39 (in TC39) refers to a group of people who have been tasked with maintaining the ecma-262 specification. New group - new number, new standard - new number. Now it's clear.