30 second skip not 30 seconds

Just got the service and was watching boxing. I've had every dvr known to man and during boxing matches when I've hit the 30 second skip, the clock on the match would reflect exactly 30 seconds but with this service it was 26 seconds. So I checked the 15 second backup and it was 19 seconds. Wonder why it is off 4 seconds both ways. Wierd.