Yeah - something definitely fishy about your numbers.
First, the SD:HD ratio used for "time remaining" is EXACTLY 7:1. Always.
Second, the displayed numbers are just two ways of expressing the amount of free space - there is NOT any separation of SD vs. HD.
Finally, the free space numbers are optimistic, and vary by the type of programming. For the stuff I watch, disk usage averages about 40% higher than it "should" be.