1) The charts are general guidelines and not accurate because the formula they use does not take into consideration a person's resting heart rate (it assumes everyone of the same age has the same resting heart rate and is of the same fitness level).
2) You have two options with regards to cardio when it comes to "burning fat."
a) Low intensity (65%-75% MHR) for long duration
b) High Intensity Interval Training for shorter durations (which would involve varying your pace/speed/resistance at pre-determined intervals, where your HR would be as low as 65%, surpass the 75% up into the 85% or slightly higher, and then you'd bring it back down to 65% and back up, etc., and so forth).
3) You can just worry about burning calories while you exercise (which means you put it back on when you eat and drink - but it does work) - and/or -
4) Consider the effect changing your LBM has on your resting metabolic rate which will cause you to burn MORE calories even at REST as well as more calories than you do now, when you exercise.
It's actually more complicated than that, but this should help get you started.