Added description in the documentation for the new parts.

Documentation/MeshBedLeveling.md

@@ -28,6 +28,10 @@ In `Configuration.h` there are two options that can be enabled.
 
 There are also some values that can be set.
 
+The following will set the step distance used when manually turning the display encoder. Default is 0.025
+
+`MBL_Z_STEP` 
+
 Following four define the area to cover. Default 10mm from max bed size
 
 `MESH_MIN_X`<br/>
@@ -55,14 +59,14 @@ When selecting this option the printer will first do a homing, and then travel t
 
 If the EEPROM has been enable it can be good to issue a `M500` to get these points saved.
 
-Issuing a `G29` will return the state of the mesh leveling.
+Issuing a `G29` will return the state of the mesh leveling and report the probed points.
 
 Probing the bed with G-codes
 ----------------------------
 
 Probing the bed by G-codes follows the sequence much like doing it with the display.
 
-`G29` or `G29 S0` will return the state bed leveling.
+`G29` or `G29 S0` will return the state of the bed leveling and report the probed points. Where X=1 Y=1 is the top-left value and X=MESH_NUM_X_POINTS Y=MESH_NUM_Y_POINTS is bottom-right value. X per column and Y per row.
 
 `G29 S1` will initiate the bed leveling, homing and traveling to the first point to probe.
 
@@ -70,6 +74,8 @@ Then use your preferred Printer controller program, i.e. Printrun, to lower the
 
 `G29 S2` will store the point and travel to the next point until last point has been probed.
 
+`G29 S3 Xn Yn Zn.nn` will modify a single probed point. This can be used to tweak a badly probed point. Specify probe point where `Xn` and `Yn`, where `n` in `Xn` is between 1 and `MESH_NUM_X_POINTS`. Likewise for `Yn`. `Zn.nn` is the new Z value in that probed point. 
+
 Note
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