Nehemiah 7:62 lists three family groups—descendants of Delaiah, Tobiah, and Nekoda—and records that there were 642 people in total from these families. This verse is part of a census taken as the Jewish people returned from exile, documenting those who came back to Jerusalem.
In the context of Nehemiah, this list is part of a larger effort to reestablish the community after the Babylonian exile. Nehemiah is recording the names and numbers of those who returned, which was important for restoring family lines, property rights, and religious duties. The verse simply notes the presence and number of these particular families among the returnees.