leeway vs exp_leeway option

[thepond...@gmail.com]

According to the README, if I want to add leeway to the check against the expiration time of a token, I can call JWT.decode with the exp_leeway option: https://github.com/jwt/ruby-jwt#expiration-time-claim

However, I also noticed that there's an option just called leeway that appears in the code but isn't listed in the documentation: https://github.com/jwt/ruby-jwt/blob/master/lib/jwt/default_options.rb#L11

What is the difference between these two options? Should I prefer using one over the other?