Update README.md

README.md

 To run this code:
-* Download `foci-annotator` which contains two folders `mcode` and  `data_folder`.
+* Download `foci-annotator` which contains two folders: `mcode` and  `data_folder`.
 * Start matlab and navigate to `foci-annotator/mcode`.
 * Open and run `annotation_example.m`. This will start the GUI on 5 images provided in `foci-annotator/data_folder`.
 
 To annotate images:
 * Left-right arrows are used to change between images.
-* Up-down arrows are used to increase or decrease radius by one (starts with five).
-* Clicking adds annotations (if in view limits and outside a previously added annotation).
-* D (shift-d) allows deleting one annotation by clicking close (less than five times radius) to it.
+* Up-down arrows are used to increase or decrease the radius by one (starts with five).
+* Clicking adds annotations (if within the view limits and outside a previously added annotation).
+* Pressing `D` (shift-d) allows deleting one annotation by clicking close (less than five times its radius) to it.
 * Zooming and panning works as normal in Matlab, but must be exited to continue adding annotations.
-* S saves annotations as a `.mat` file and a `.txt` file with csv formatted text. NOTE: previously saved files will be overwritten.
+* Pressing `s` saves annotations as a `.mat` file and a `.txt` file with csv formatted text. NOTE: previously saved files will be overwritten.
 
 Each row of the data contains one annotation given by: image number, transverse (x) coordinate, axial (z) coordinate, radius (in pixels).