Daily Return on Investment has to do with how much profit you'll make each day you own the bond. So if a bond chart shows DROI= 2% then it means you're making 2% a day on that bond. If the bond is adjusting in 10 days, that works out to be a 20% take in the 10 day period, which is not a bad return...
It's basically a way to help you calculate if the money you are investing is worth the time in which you own the stock. Perhaps you could make MORE money in those 10 days by daytrading the same amount of money, or by playing openers, or other ways.
It merely allows you to see if the cash you are tying up for 10 days is worth it on a daily basis, so you can decide if you WANT to tie the cash up.
Daily Return on Investment or DROI is helpful for some players to decide if the money they are spending is worth the time they have to wait to earn the profit.