Jim claims there's no 13th floor by looking at the elevator display, yet there is a 13th floor call button on the panel.
The meeting with the four men in the back of the shoe store breaks up. As Jim walks out of the back room the front store windows are completely dark yet when Jim and Billy walk onto the street it is bright sun.
The fire truck which is used is shown using a 'Q' siren which has a distinctive sound. That model of fire truck uses a different model siren.
Jim says he counted 16 floors on the building, but if it had 16 floors and they skipped the 13th floor in the elevator, then the top floor in the elevator would be floor 17. He should have counted 15.
In reality, many building owners have a superstition about the 13th floor and a 15 story building will number floors 1-12 as 1-12, but the 13th is 14, the 14th is 15, the 15th is 16. However, the Waterbury elevator lists 1-12, 14 & 15, so it would have been perceived as a 14-story building (17 never enters into it), presumably to hide the 13th floor from public perception. They haven't mislabeled anything, only programmed the elevator to not stop at a floor they claim not to have. Still, Rockford should have counted 15.