As I mentioned several times regarding Garmin 1030 1040, this data field does not behave correctly. It works only when turn by turn navigation is switched off. When TBT is on, this field shows ascent to the next navigation errow. So after years of complaints I sugest Garmin to:
1) rename the field the way "ascent to next something"
or
2) explain the idea that stands by this ibehaviour and say that it is correct and done deliberately by design
or
3) correct this field
This field is useful when navigating on long rides when ascent to the next pub/water/summit is more important than their dinstance.
Thank you Garmin