Update:车胎Rotation

Well, I went to another store of Discout Tire and simply asked for rotation. The guy took measurements and said nothing.  In 30 minutes, it's done.

Thanks for your input.  I am thinking the first store I went to may have some issues.  Actually, when I asked more about how worn out the front tires were and how the mechanic measured, he was kind of unsure and had to ask another mechanic to support him.