It is something like "months must be averaged in order to get the final result". Imagine that you know the benefits of a company in January, February and March. If you want to "promediar" these three months, you have to do the next operation: (Jan+Feb+Mar) / 3 = x "x" is the result of that "promediación". I hope this can help you.

if you translate literally .....( it must to average each month to get the final result).