Stopwatch with Pause/Lap  6 digit 7 seg LED. HELP!

I'd like the full-up please, as I have been helping him & I am stumped as to why it would be so inaccurate. I have a 10 minute countdown timer, which I have not timed for accuracy, but works on similar principal (only rolling backwards required a lot more current state checking to decide if the digits should roll or not).