In the Notes section of the description for this kata it says that there is a preloaded dictionary you can use, named NATO.

All classes come from some super class, you need to lookup ancestors also lookup the RUBY docs, Integer inherits methods from its superclasses.

class numeric has step method

I am new to Ruby - I'd expect the min parameter to be an integer, but the integer class doesn't have a step method. What gives?

https://ruby-doc.org/core-2.5.0/Integer.html