So that the Community can help you better, we need to know exactly which Canon camera model you're using. That, and any other details you'd like to give will help the Community better understand your issue!
If this is a time-sensitive matter, search our knowledge base or contact our US-based technical support team at http://canon.us/SupportCF
Thanks and have a great day!
The histogram for *both* is an approximation since it displaying a histogram for the jpeg from the internal JPEG engine. I can easily believe that the LiveView histogram is a histogram of the live view display which is a speed-optimised jpeg/video display, *not* the fully-processed JPEG.