The finding is that it is possible. Not everybody is able to perform it, though. It's difficult to stay focused and aware when lucid dreaming - it takes practice.
how do you even get 18% from 36 participants? 7/36 = 19.4% and 6/36 = 16.6%. I know they said "roughly" but I don't see why how you could round to that number.
Possibly a combination of rounding all the numbers and having the constraint it must sum to 100%
Could be that each dreamer participated in multiple trials