Extraction of mask pixel values

Hi all,
I am extracting mask pixel values from an image in snap. After extraction, the extracted file contains columns for Pixel-X, Pixel-Y and all band values. In Pixel-X and Pixel-Y columns it gives x and y coordinate position which is showing floating point value i.e e.g 286.5, 340.5 respectively.
I am not getting why coordinate positions are stored with floating point values. If anyone knows reason behind it, please let me know.
Thanks in advance.