Updated 05-May-2020.
Mondo shtuff from around the internet, all about ARROBA!
My botty best at summarizing from Wikipedia: arroba was a custom unit of weight, mass or volume . it is still used in Portugal by cork merchants . modern metric armroba is defined as 15 kilograms (33 lb) Bolivian arroba is equivalent to 30.46 litres (6.70 imp gal; 8.05 US gal) in Peru and 11.5 kilograms (25 lb) in Bolivia . however locally there are many different values