BugkuCTFtutorial - PNG Steganography | Misc

The writeups of pngcheck and pngcsum that I found :https://github.com/Alpackers/CTF-Writeups/tree/master/Misc/Defcamp%20CTF%202015/Misc/She%20said%20it%20doesn't%20matter The tools I used to this problem: binwalk,stegsolve.jar ,foremost,jstego.jar,exiftool,zsteg,strings,hexeditor,pngcheck,pngcsum. The part of writeups which I don't understand,I'll try to figure it out. Thanks for watching :)