This edit suggestion was approved although it was rejected by a user, and no other votes were cast.
According to suggested edits FAQ:
Three accept or reject votes are required to approve/reject an edit.
So, what caused this edit to be approved?
This is fixed now. We recently introduced a bug in which if the question asker with <2k reputation approved a suggested edit, then the "approve" review wasn't correctly recorded.
In other words, if it weren't for this bug, this suggested edit would show
David Liu reviewed this [some time ago]: Approve
We'll try to get the bad data cleaned up.