Even if the engineers didn't include it in the procedure, Watney would know to count all the fasteners he removes from the capsule and make sure they're all discarded OUTSIDE the capsule before launch to prevent injury from them bouncing around like bullets inside during ascent.
Early in the film Watney takes an inventory of his food supply.
The shot immediately after shows him finishing the line, and gesturing.
Watney is exploring the storage cabinets in the base and then eats while itemising his food supply.
The cover shows Fernando at the top of the tracklist but the first pressing only had Fernando as a bonus track and it wasn't listed on the cover. A scientist like Watney should have realized that the hexadecimal system he uses with Pathfinder is unnecessarily complex - Watney complained that using a full alphabet would give him only 13 degrees of separation between letters, but with sixteen hexadecimal characters (plus the question mark he adds), there's only 21 degrees of separation between characters, and hence still a high risk of ambiguity.
There is next a cut to him flushing the toilet in which he seems to have the idea to go back to a cabinet and so he discovers the potatoes.
It's clearly out of sequence as he is dressed differently in the toilet sequence and is chewing in the two scenes either side.
Watney could have made an alphabet with only six characters - NASA could represent 36 different values (all 26 letters and 10 digits) using two characters per value (same as ASCII), and Watney would maintain 60 degrees of separation between characters and thereby eliminate risk of ambiguity.
NASA can see Watney, so Watney could have written out an explanation to his base-6 code for NASA to follow.