While MPL reads the model file, the status window displays the name of the file being read, the number of lines read so far, the number of variables and constraints in the model, and how much memory has been used. While the optimizer is solving the model, the number of iterations and the value of the objective function are shown.
If MPL finds a mistake or an error in the model, an error message will be displayed. It shows the erroneous line in the model with short explanation in plain language of what the problem is. The cursor will automatically be positioned at the error in the model file, with the mistake highlighted.