The Abstain feature was discussed extensively at https://gov.bancor.network/t/snapshot-feedback/2897.
Here is an example of how FOR and AGAINST percentages, as well as Quorum, are calculated:
FOR: Number of votes casted FOR Percentage: (FOR / FOR + AGAINST) AGAINST: Number of votes casted AGAINST Percentage: (AGAINST / FOR + AGAINST)
ABSTAIN: Number of votes casted ABSTAIN Percentage: ABSTAIN / (FOR + AGAINST + ABSTAIN)
QUORUM: (FOR + AGAINST + ABSTAIN) / TOTAL STAKED vBNT
Note that neither FOR nor AGAINST option is taking into account the ABSTAIN option. We as a DAO can use these to know whether a vote has supermajority requirements (66.7% or greater).
With real numbers, this would look like the following:
10,000,000 TOTAL STAKED vBNT (for voting) 2,000,000 FOR votes (80%) 500,000 AGAINST (20%) 4,000,000 ABSTAIN (61%) (2,000,000+500,000+4,000,000) / (10,000,000) = 65% QUORUM
A dummy proposal was created on the Bancor snapshot to test the Abstain feature and can be found here.
FOR Activate Abstain feature.
AGAINST Don't activate the feature.