A question in the viva cannot prompt you to talk in minute detail about the sum of three or more years of work. Every response for every question that you are asked will take up a few hours at most.
A response could be short because that’s what it needs to be. It could leave details out because they aren’t as important as what you keep in. It could be incomplete because the complete details would take too long, or you don’t have them, or for some other reason.
A response may or may not be an answer to the question. It may or may not move the conversation in the direction you or your examiners want. It may be that you have to stop before you really want to, or just give an indication of what you mean, rather than the full picture.
Remember: you can always pause and think, and your examiners can always ask for more if they need it.