I would have just said that, 'there is other stuff there', but first I would have suggested and changed the computer to single clicking where possible. What is just an automatic action for most of us, double clicking for an older person who has never used a mouse can be very quite difficult.
Once you are an experienced computer user, it can be difficult to unlearn things you do automatically, so that you are on the same level as a novice.
Another reason is that no two computers are set up in the same way, so you have to learn where things are as you are teaching. And never mind different operating systems. And, and, next lesson, they will have been fiddling!!! and altered things.
All too hard.