The fix levels
Standalone uses satellites alone; differential uses corrections. RTK float is not fixed. RTK fixed does not by itself guarantee accuracy; check the accuracy estimate and conditions too.
The phone's own GPS is usually good to a few meters under open sky.
The app calculates the horizontal estimate from the receiver’s GST accuracy values. It is not a guaranteed distance from the true position. Without GST, accuracy is shown as not reported. A fixed status alone does not guarantee accuracy: check the estimate, base distance and sky. GPS points keep their accuracy; the result shows average, worst and ignored points. The GPS quality requirement controls filtering.
Heights
Each point keeps the height the receiver reports. Technical details shows the altitude above sea level, the geoid separation and the ellipsoidal height. DXF exports keep each point's height as Z, in meters.
Coordinates and reference frames
Correction services can use different reference frames, shifting the reported coordinates. Check the service’s frame and epoch. Keep the same service for repeat work on a site.
Not a legal survey
Even with RTK, the app is a measuring and estimating tool. Do not use it to establish property lines, settle boundary disputes, or replace a licensed surveyor.