When I used to do manual labour, I used to do this when told to do tasks. e.g. if someone said "Go and sweep the leaves and put them in the bin", I'd clarify and say "So I'm sweeping those leaves and putting them in the bin?".
It worked well in making sure everyone was on the same page about what I was actually supposed to be doing. I eventually stopped doing it though because people got annoyed and thought I was stupid or just not listening to them, which was ironic because that's exactly the opposite of what was happening.
It's a shame really, because it did minimise errors. There's nothing more annoying for everyone then when someone spends hours doing the wrong task because of poor communication.
What I do when I want a final confirmation that I understood right is say what I'll do instead of asking. In your example, it would be, "Ok, then I'll sweep those leaves and put them in the bin."
But, who knows, it might not have made a difference. In my case, my boss already knows that I like to be extra certain that we're both on the same page.
That's an important distinction. If you sound like you're questioning every instruction or you don't understand the tasks then your boss is going to get frustrated with you.
If you have a poor memory like me, repeating things back is important to help you remember them too. Since I work in office type environment, I try to repeat things back by writing them down where both the requester and I can see them - such as in a job ticket or email. This also helps if a third party joins the task later or if the task gets put on hold.
Whereas at the automotive shop I used to work at, everyone else picked that habit up from me. I'd picked it up from experience in aviation line service during high school. My coworkers acted annoyed for the first week, but they quickly realized I didn't expect a response and it made communication in a noisy shop clearer.
Especially after the day that a coworker got confused about which truck was which, and drilled a 3.5" hole in the bed of a brand new truck (thinking it was getting a gooseneck hitch). After that, everyone else started repeating verbal instructions as well.
I do this also at my office -- it massively helps avoid misunderstandings, errors due to miscommunication, and other screw-ups. Like Hamlet said -- 'we must speak by the card, or else equivocation will undo us!'
I totally agree that the method you are using is a good habit. I noticed that cashiers often call out the denominations of money I hand them for a purchase, which too helps. I used to deliver newspapers late at night and once lost count (while counting in my head) of how many heavy bundles that I had loaded from one truck to another, which required me to start over - and on a cold night too. Thereafter, I picked up the habit of counting aloud, especially if somebody else came by and distracted me.
Cashiers in Japan always count out loud both what they receive and what they give back.
Cashiers in my home country never do. And sometimes I forget what I handed over.. it would have been useful then to have the verbal confirmation. Not to mention the time in Mexico when a gas station employee tricked me.. oh well, maybe not, in the latter case.
It worked well in making sure everyone was on the same page about what I was actually supposed to be doing. I eventually stopped doing it though because people got annoyed and thought I was stupid or just not listening to them, which was ironic because that's exactly the opposite of what was happening.
It's a shame really, because it did minimise errors. There's nothing more annoying for everyone then when someone spends hours doing the wrong task because of poor communication.