When I preview an image in windows, the properties panel says my file is only 958KB with dimensions 2400 x 2369. But when I open the file in photoshop (I have CS6) , it says my file is over 16MB with the same dimensions. What is going on?
The file content will be compressed, making the file smaller than the uncompressed image size being reported by Photoshop.
Photoshop is telling you the quantity of bytes consumed by a composite of the document it has open: 2400 px * 2369 px * 3 channels (R,G and B) * 8 bytes per channel = 16MB.