I have limited experience in Photoshop, and am working with a file with two other people. We are creating web comic pages. The line artist and colorist are both using CS 6. I have CC. The file I receive from them is around 238MB. If I open it and make even the slightest edit, Photoshop will not save it as it warns that the file size is too large (greater than 2GB!). How does this happen? Is it something in my preferences that causes 10x increase in file size?