Body signatures (which is your body’s shape reflected in the mattress), in modern beds are normal and are generally an indication that the comfort layers are working with your body as they should.
To determine if an impression is normal you would need to take a measurement. Place a long, straight edge, like a broom handle across the mattress surface. Measure from the underside of the straight edge to the top of the quilt design, not the stitching line. A measurement of 32mm or less would not indicate the presence of a manufacturing concern with your mattress.
Body signatures may appear to be more pronounced with King Size mattresses. Utilising the entire surface of your mattress and rotating it as recommended in your Sealy Guarantee/ Warranty will assist in providing even wear, particularly during the first one to three months of your mattress life. The base that your mattress is on may contribute to more pronounced body impressions forming.
Sealy does not recommend putting a new mattress on an old base and strongly recommends purchasing a Sealy ensemble (both mattress and base). If the base is a slat base, this could also influence the performance of your mattress. Sealy suggests that the slats be secured with a centre support rail and leg, with the gap between the slats smaller than the slats themselves.
To work out whether your base is the problem, one suggestion is to take the mattress off the base and try it on the floor. If the impressions are less evident, this may indicate that there is a problem with the base.