Pace and distance calculations.

[sprnza]

Hi there!
I try to analyze GPX tracks I exported from ForRunners. I use gpxpy and I definitely get differences in pace and distance calculations. Here is the gpx.
gpxpy reports:

Name: Test Name
Start: 2018-02-25T03:57:35
End: 2018-02-25 05:03:33
Duration: 65.97 mins
Avg. pace: 5.09 mpk
Length: 12.97 km
Km: 1.0 Avg. pace: 5.16
Km: 2.0 Avg. pace: 4.82
Km: 3.0 Avg. pace: 4.92
Km: 4.0 Avg. pace: 5.29
Km: 5.0 Avg. pace: 4.97
Km: 6.0 Avg. pace: 4.95
Km: 7.0 Avg. pace: 5.08
Km: 8.0 Avg. pace: 4.76
Km: 9.0 Avg. pace: 5.33
Km: 10.0 Avg. pace: 5.26
Km: 11.0 Avg. pace: 4.76
Km: 12.0 Avg. pace: 5.13
Km: 13.0 Avg. pace: 5.67

ForRunners stats: summary, pace stats

What's a secret? How could I get the same results? Another android app in wich I used the imported GPX shows the same results as gpxpy does. Does ForRunners make mistake?

[brvier]

Due to low precision of some device's GPS, some rounding and filters are used. Exported GPX have full raw data without this filters. Not sure if gpxpy have filter too.

I need to investigate a bit more.
Also which version of ForRunners did you use ?