Total number of members of the club = 333
Two Thirds majority is needed to pass an amendment.
So, the total number of votes needed to pass an amendment =

This means, an amendment will pass only if it receives 250 or more votes. The faction is sure about 191 votes. In order to pass the amendment the faction needs 250 votes.
So, the number of votes which the faction will need more= 250 - 199 = 51
Therefore, the faction needs 51 more votes to pass an amendment.