Bytes in/out not correct

Hi, 

I'm using Joy to analyze flow.  The bytes in/out output json file are not correct(orders of magnitude difference), by viewing same statistics in Wireshark. Please let me know if Joy was not properly used. 

My usage of Joy:
`joy bidir=1 tls=1 dist=1 zeros=1 retrans=1  xx.pcap | gunzip >joy_result.json`

Thanks. 
