One of the main purposes of data hiding is to secure the messages while transmitting via a public network such as the internet. As known, there are so many types of data hiding such as hiding text inside text, text inside video, and text inside digital image. It is also known that, Difference Expansion has become a powerful method in data hiding using digital images. For instance, it is known that data hiding is needed in so many fields such as health, military, and finance. Especially for reversible data hiding which has the ability to return the same secret data and cover image after the extraction operation. In this paper, we focus on how to increase the capacity of the secret message as high as possible while maintaining the quality of the stego image. We will present a scheme that has modified the previous method by enlarging the pixel blocks to be as a matrix 4 by 4 that can hide 15 bits per block. In addition, we have modified the scheme of RDE to make the difference values smaller since that will bring also a chance for increasing the capacity and may improve the quality of the stego image. The experimental results have shown that the capacity has surely and hugely increased.