Anatomy of "All Day Pace"

I had tons of issues with my Garmin yesterday.
Most of them due to the fact that: I forgot to turn it on, or back on after water stops, or I would press Lap split instead of STOP.  Despite all that, here are most of the mile splits, not how my pace goes to hell towards the end as soon as I hit the Town Lake trail that I hate so much.  Those slower paces felt like a snail would be passing me at any moment. (no offense to anyone that reads this.  paces are relative.  You'd feel the same running 30-45 seconds slower than yours)

The 9:22 is due to walking while eating and drinking stuff after a water break.
There's a 8:34 right at the end, but that's because I got a good song, and some guy ran by and I could sense he thought his 8:45 pace was cool, so I had to show him who's boss even though I was at 32 and he was probably at mile 3. "Don't test me, weekend jogger."

 08:48.1
 08:24.5
 08:17.4
 08:29.6
 08:29.7
 08:38.9
 08:30.8
 08:31.9
 08:28.9
 08:00.4
 08:22.4
 08:12.7
 08:14.3
 08:04.2
 08:15.1
 08:11.5
 09:51.5
 08:43.6
 08:14.5
 08:11.9
 08:14.5
 08:21.3
 08:20.9
 09:09.9
 08:23.2
 08:24.5
 08:22.7
 09:22.5
 08:59.7
 08:34.7
 09:02.1
 08:49.0

Finally, this is weird...
When i map out the route on GMAP, it comes out to 35.35 miles, but on my Garmin it's almost 1.5 miles less. I may have to start thinking that I accomplished 35.