diff --git a/python-core.tex b/python-core.tex
index 311ad0f..e565a4a 100755
--- a/python-core.tex
+++ b/python-core.tex
@@ -2057,6 +2057,7 @@ plt.imshow(rgb_image_float)
 from PIL import Image, ImageDraw
 image = Image.new('RGBA', (200, 200))
 draw = ImageDraw.Draw(image)
+# bounding box coordinates for the ellipse topleft, bot right (x1, y1, x2, y2) 
 draw.ellipse((20, 20, 180, 180), fill = 'blue', outline ='blue')
 draw.point((100, 100), 'red')
 image.save('test.png')