First, make sure your units aren't changing. There is a big difference between 67MB and 67Mb. One B is equal to 8 b's, so if you are paying for 67Mbps and you are getting 6MB, that's pretty much ok. 64/8=8. You are losing speed somewhere, but you are for the most part getting what you should. You should also make sure you are testing correctly. NOTHING else using the bandwidth and test with a speed testing site. Not trying to download something and see what comes through.
67Mb is an odd rate to pay for. Are you sure about the 67?