tariff miles wtf

I have only been driving a few months and am still learning about how big companies are finding new ways to screw the people that work so hard for them. I understand that alot of companies will not pay the hub miles of a trip, someone told me that its the way the companies bill the customers from zip code to zip code and its usually just a few miles { less than 10 } off. I took a load from Montose Colorado to Denver and then to Sumner Washington and followed the routing they gave me and the hub total was 1666 miles but they only paid me for 1559 and when I asked why there was such a big difference in miles, I was told I was paid tariff miles. I was wondering if anyone else has experienced this from big companies, I think its BS, I dont think they would like it if I only drove those miles that they are paying for and then shut the truck off, but man I sure feel like it.