The track is divided into five sections. Graphs of all individual sections are OK. But when I select all of them suddenly it seems that the distance data on one of these tracks are wrongly interpreted and displayed in kilometers instead of in meters.
I was trying to post .gpx files by copying them here - there was a message Upload file(s) but I cannot see any of them
OK I got it - just images - four tracks are longer than 1 km, one - the "offending" - track is long less than 1 km - distance on an individual graph of this track is in meters but on the graph where all the tracks are selected and opened together meters are interpreted as kilometers