It's actually 1/7th of an orgasm.
However the orgasm itself will never come, nor will the feeling of an orgasm, as you can't sneeze 7 times at once. And to make it 7/7ths, you would have to have them all at once.
One after the other is 2 lots of 1/7th, and not just 2/7th. lol!
When we did this in science, some of the kids were trying to make themselves sneeze loads under that presumption!
Hope that makes sense.............