Cisco Firewall :: ASA5585X - Packet Rate On Inside And Outside Interface Doesn't Match

I am doing some per-deployment testing with a ASA5585X and noticed that when I feed it a stream of SYN packets on the outside interface the measured traffic rate on the inside interface going out is about 10x the rate of the outside interface going in.
 
laptop ---  ASA --- PC
 
I send 6k TCP SYN pkt at interface rate from the laptop targeted at PC. No packets are dropped by Ac Ls or policies and can be sniffed at the PC.
 
Show interface commands show:
sh int inside:
... ...
  Traffic Statistics for "inside":
...
1 minute input rate 23 pkt/sec,  1303 bytes/sec
1 minute output rate 4454 pkt/sec, 820757 bytes/sec
  
sh int outside:
... ...
Traffic Statistics for "outside":
...
1 minute input rate 885 pkt/sec,  70847 bytes/sec
1 minute output rate 7 pkt/sec,  425 bytes/sec
 
I would expect that if 885 pkt/sec enter the firewall on the outside interface the same amount or less would exit it on the inside...? Why this is not the case? The packet rate is about 5x and the data rate is about 10x greater.