Thank you so much Petrov 20 4, 8:24pm

to be more percise- that desicion came because Petrov had 2 big reasons to doubt that computers were correct.
1- that computer system had had some issues prior to that
2- By his estimates, americans wouldnt have launched so few missles.
Therefore he decided to wait until radars confirmed missles, although at that point it wouldve been too late to retaliate. His gamble paid off