Edge angle is the measure of the acuteness of the angle formed by two edges of a quadrilateral element. A small edge angle typically occurs with long, thin elements. When the edge angle becomes too acute, the quality of the element is lower and the solver you use may have difficulty.
Creo Simulate considers an ideal edge angle to be 90. However, because this ideal is too stringent for most models, the software uses an edge angle of 30 as a default for this quality measure.