Hey guys, this is my first post on the forum. I recently bought the hptuners pro suite, NGK wideband and purchased the tuning schools basic course for gm vehicles as well. I've been going through the courses and up to this point my only experience in seeing log files are from those courses. I decided to log my 2008 silverado with a 5.3 and 4l60 on a drive and was surprised to find at one point it had knock retard of 5 degrees. I looked over the charts and it seems that any time the absolute load (SAE) exceeds 50 percent, there is some sort of knock retard present. The amount isn't consistent. At a specific event the degrees of spark swings from 28 to 7 and then back up slightly before knock retard kicks in directly at the end of the "event". This occurs while my throttle position percentage has been constant and my load has remained constant. I'm just trying to make sense of some of the things I'm seeing in this stock tune 5.3. Any insight and advice would be greatly appreciated. Thanks in Advance.

I tried to attach the log how I thought I needed to. If I've done this incorrectly just let me know.
The event I refer to occurs at 6:19 in the log.
2008 silverado 5.3 4x4 4l60 drive home.hpl