I had a very interesting situation recently. I think this is the best example that explains what is misunderstanding. It also shows that even very obvious things for you can be interpreted or understood completely differently by other person.
So, please make sure that you are understood correctly to avoid any problems in the future.So, here is the real life situation for your judgment 
We have two people - A and B. Everything happens on Sunday, May the 1st. Person B already knows that it’s May.Person A is watching a TV and takes a look at the watch, where he sees the date April 31 and starts doubting if it is correct… Here is the conversation:
A: How many days in this month?
B: 31 days
A: Ok (Thinks that everything is correct)
- Meanwhile BBC channel shows May the 1st demonstration in Berlin. A is a bit astonished and confused…
A: Ehm… so it’s not April already …
As we can see all decisions were made based on assumptions without providing more detailed information from one side or asking clarifying questions from another side.
Make sure this doesn’t happen in more complicated situations, cause since decisions can go to the opposite direction.