When is 3 a 4 and 5 a 6

Ok so doing a pedi case today and every time a pressure was called out the MD did not agree with the pressure and said it was one millimeter of mercury (mmHg) different that what we measured it as.  So if I said the RA presure was 8 the MD said it was 7 if I said the PA was 12 the MD said it was 13 and so on.  Ahhhh but I am smater that the average bear.  If I measured the pressure at say 8 then I would tell them it was 7 so they would say no it is 8.  Some people are just control Freeeeeeeeaks.