HI Ryan For the most part I think the numbers should fall within a range of 50 to 85 and I think the most important thing is that the numbers between the min, avg, and max are all fairly spaced apart. The avg shouldn't be too close to the min or max. So for example Lets say your readings are 57, 63, and 75. The difference between the min and avg is 6, and the difference between the avg and the max is 12. That would be pretty good. What you want to avoid would be to have readings like 57, 60, and 90.
Ryan are you asking a general question of something specific? You don't mention what electronic device. Magnetic declination is the value that is used to align a magnetic compass with true north. In my part of the US it is about 8 degrees.
Thanks Guys, just refreshing my memory on Mikrokopter. My readings were pretty equal, 58 68 79. Just upgraded to MK 2.10 from 2.06 and also moved my external compass in off of an extra boom on my x8. My Magnetic field readings have a little more variance than before, 99 104 106. Instead of 101 102 105. I saved about 200grams removing the extra boom and mounting gear.