I pulled 30 cigars from a humidor humidified to 70% RH using a HumiForm for over a year. The cigars were taken from different levels inside a 100 stick humidor, and their individual humidity measured using a CigarMedics Humidimeter. The cigars on top were brand name cigars in cellophane wrappers, while the cigars in the middle and bottom of the stack were un-named and unwrapped. The caps averaged 64% while foots averaged 62% humidity.
According to the HumidiMeter manufacturer, the reading at the foot of the cigar will always be lower because the foot is open and moisture will enter/escape through the foot. It's also possible to test the head of the cigar which will give you a higher reading as the moisture is "trapped" by the cap.
You will also notice that different types of cigars will give you different readings even if they have been in your humidor for equal time due to how the different tobacco leaves hold moisture. We found that many customers prefer their cigars to have a foot reading 60%-65% because it will increase as you smoke the cigar, but this is all personal preference