I noticed decimal values in mathematica have about 17 places of accuracy and then a whole bunch of random numbers. If you put a number in that 18th place mathematica will change the number to have 10 more zeros as buffers before the garbage. Unfortunatly it doesn't do this all the time and some of it depends on the accuracy you ask for as well.
I noticed this doing calculations with decimals where I had 17 digits of accuracy and putting a zero in the 18th place gave me a different result which should not happen.
Try the following to see what I mean