why does a void function have a return value

[enst]

account-authorization-requested
void (*account_authorization_requested)(PurpleAccount *account, const
char *user);
Description:
Emitted when a user requests authorization.
Parameters: account The account.
user The name of the user requesting authorization.

Returns:
Less than zero to deny the request without prompting, greater than zero
if the request should be granted. If zero is returned, then the user
will be prompted with the request.
Since:
2.3.0