In the end of the first movie we see that Marty could not start the engine of the DeLorean when the alarm clock rang. Doc had calculated the time required by the car to reach the lightning wire exactly at 10:04PM, but Marty started moving from the start line several seconds after the alarm clock rang.
Is there any explanation on how the DeLorean, nevertheless, hit the wire at the exact moment? Did doc miscalculate something? Or did Marty somehow go faster than Doc expected?