To calculate the area of a parallelogram using a determinant matrix, the absolute value of the determinant of a 2x2 matrix formed by the vectors is used. The correct matrix is constructed from two adjacent vertices of the parallelogram. In this case, confusion arises from using different pairs of points, leading to inconsistent determinant values. The area should match the geometric calculation of the parallelogram's dimensions, which in this case is 30. Identifying the correct vectors and ensuring proper matrix formation is crucial for accurate area calculation.