Thus far distributed.net has proven that the existing best known rulers for OGR-24, OGR-25, OGR-26 and OGR-27 are indeed optimal and the only rulers of such lengths to be so.
During an OGR contest, the client does not attempt to compute or determine the "optimality" of the rulers it is evaluating. It instead only evaluates rulers to see if they are better than the best ruler speculated by mathematicians. As soon as a ruler (node) is determined to definitely be no better than best-known one, full computation of that ruler's optimality is discontinued and the next node is attempted. As such, the client will only transmit a "success" when it believes it has found one that is equal or better.