What is waypoint ALT actually telling me?

Thanks for having me in the group, I am an experienced fixed wing and VTOL pilot, but not used to using Ardupilot. I am programming a VTOL mapping mission for a particularly tricky location and I am wondering how I read the WP altitude in mission planner.

In the example above, the altitude column for WP103 says 191m, but the SRTM altitude for that point is 260m AMSL so I would have thought either the WP alt should be 120m (the height I set above the terrain) or 380m (the AMSL height plus 120m). So what is the 191m about? Should I be concerned that it will fly my aircraft into the side of the hill at WP103???

I just recently started practicing with terrain following with my fixed wing craft using the simulator with xplane11. I dont know where your home is or its AMSL, but you have verify height checked and I think that can affect the altitude setting of way points. One thing I use if I’m unsure of my flight path altitude is right click on the map>map tools>elevation graph. That should show your flight path relative to the the terrain if it followed your points exactly.

You set your mission heights relative to start point.
You can change to terrain if you want