How do you level a surface in both directions?
Place the phone flat near the centre of the surface. Tap Check Surface, then wait a second for the reading to settle.
The bubble moves toward the higher corner. Lower that corner, or raise the corner opposite it.
Work on one direction at a time. Move the bubble onto the centre line first, then move it along that line into the middle ring.
Adjusting all four feet in turn takes much longer, because every change moves both directions at once.
What do the three numbers mean?
Total lean is the large number. It shows how far the surface is from level, in whichever direction it falls.
It has no plus or minus sign, because a slope has no direction until you choose a side to stand on. A reading of 3° across and 4° along gives a total of 5°, not 7°.
Across and Along show the two directions you can adjust with feet or shims. Drop per metre converts the total into millimetres.
For a stand with three legs, line up one edge of the phone with two of the legs. Level the surface using those two, then finish with the third leg on its own.