Why returning nagetive position when I set binlogPosition greater than 4?

[xhyzjiji]

code: return first event by the specific position

OpenReplicator or = new OpenReplicator();
or.setHost(host);
or.setPort(port);
or.setUser(user);
or.setPassword(password);
or.setBinlogPosition(binlogStartPos); // greater than 4
or.setBinlogFileName(binlogFileName);
or.setBinlogEventListener(new BinlogEventListener() {
@OverRide
public void onEvents(BinlogEventV4 event) {
list.add(event);
// notify external thread to stop openReplicator
}
});
or.stop(xxx);
return list.get(0);

Then, I get binlog event like this:
event pos=-116 <--- first event
event timestamp=1517369647000
event pos=8808036 <--- second one is correct
event timestamp=1522235789000