What exactly do you want to do with that int? Can you post a code example?
In general terms, from the type system’s perspective, there’s a possibility that number[0][0] is None (or, in JS/TS terms, undefined). So you have to handle this case somehow. See Null, Undefined and Option, for starters.
I’d also be interested in an example.
What does the data represent? Do you want to aggregate / count the numbers in the inner array? why do you want to do [0][0] accessors?