When you run a design study, the Structure engine performs calculations and increases the polynomial order for each element edge until the convergence criteria are satisfied. (The polynomial level for edges on which beams and 2D shells lie begins with either the third order or the order you enter on the analysis definition dialog box, whichever is higher).

An analysis converges when the difference in the results of the current pass and the previous pass is within the percentage you specify under Convergence.