A much clearer way of writing the exact same code would have been to use sprintf:
title(sprintf('Final Return = %.3f (%.3f%%)', sum(r4), sum(r4)/mean(series2(1, :))*100));
Each %.3f in the sprintf is replaced by the numbers that follow the string, in order. To write a % sign in the string, you need to escape it, hence the %%.
It basically writes a title like: 'Final Return = 12.200 (15.750%)' assuming a sum of 12.2 and sum/mean of .1575.
