That "7% of how we communicate happens with our words. The other 93% is NON-VERBAL" is false. If that were true, deaf people wouldn't have ever needed sign language.
A lot the questions are (and this is for any job): "What have you done in the past when x happened?"
With an office assistant, that's usually questions dealing with prioritizing tasks and handling difficult people. Prepare your answers in advance. Write yourself a few stories to prepare yourself. You don't want to sound rehearsed, but you do want to know you sound like you're confident in what you're talking about.