The other two replies are exactly correct and I’m not going to add any new facts. All I’m going to try to do is simplify those comments a bit.

This is the root of the problem: a charlist can be thought of as special sort of string and it’s just a list of integers… which is indistinguishable from any other list of integers where you really want just the numbers. Because Elixir can’t always tell the difference between a list of integers which is just a list of integers and a list of integers which is meant to be a charlist is makes a default choice when it comes to displaying the list: treat the integers as ASCII values and print those characters. In your case it’s wrong, but as the others said, its just a display issue: your list of integers is there as you intended and will work the way you intend outside of this output behavior. Importantly, note that the actual list and its values are not transformed from what you expect: this is just the way your values are interpreted for display.

This is the way to change the default output of that list. In your case, (assuming you’re using IO.inspect/2), the default assumption that a list of valid ASCII codes is ASCII is wrong and the option described above changes that default assumption for that run of the function. This doesn’t change the actual list values, that’s always the [55] you intended, just the way they are displayed.