When the group arrives to Atlas Academy, Alex explains to Topher the plan to obtain the computer. Alex tells Topher the combination to the safe holding the computer is "19-3-26." Back outside, when they run into Topher and are surprised he has the computer, he explains he used the combination "19-26-3." Maybe it was cut from the episode, but it's never explained how he actually got it and why he said the wrong combination.