Determining 2/3 vote number with decimals
If you are concerned about precedent, then it is best to say that one must round up to the nearest whole number. What happens when you have 190 people voting for and need 193? Will you look back on this decision and say that there is now 0.33 wiggle room?
The peace of the house must also be considered. If either side becomes distressing, it could lead to a major split in the unit. The greatest compromise would be to allow for another vote. Before the vote, the members would agree what number of votes is sufficient in this one case, and would argue their side again.
