Hping showing -400% packet loss
why only 1 packet was sent when "-c 5" is set
Did you read the man page? That's exactly what it's supposed to do.
how did it receive 5 packets
We don't know - if you run tcpdump or wireshark then the reason might be a bit clearer. If it took a long time to return, then most likely the remote host is resending the syn-ack packet.
what does -400% packet loss mean?
100 * (packets sent - packets received) / packets sent
= 100*(1-5)/1
= -400