The number 13 is a fairly significant one. Whether that significance is good, bad or indifferent is up to the person interpreting it.
The tarot card XIII is “death,” often depicted as The Pale Horse from the Four Horsemen myth. Whether that’s literal or figurative, it’s a dreaded card which oft brings anxiety to the customer getting the reading.
The number 13 is fraught with tension in Catholic circles. 13 disciples were seated at the Last Supper, but Judas Iscariot ends up being a double agent, turning Jesus of Nazareth over to the Roman authorities in Jerusalem for 40 pieces of silver.