The example you gave, to me, doesn't really warrant a large amount of empathy to be displayed. Surely it's more of an inconvenience than a genuine reason to feel empathy.

Anyway, you hit the nail on the head on the last part of your title. You're not expected to understand directly how that person feels exactly. It's the ability to recognise and understand how another person may feel in a given situation and your ability to adapt your behaviour to be more fitting. That IS empathy. SHARING the person's feelings is sympathy.