Use the Shape Optimization Criteria dialog to change the Target Mass from the optimized default, Auto.
On the Simulation Setup tab, click (Shape Optimization panel> Shape Optimization Criteria) to open the Shape Optimization Criteria dialog.
In the Shape Optimization Criteria dialog, in the Target Mass row, click in the Value column to activate the entry box.
Using the up/down arrows, switch to the numerical value, then modify it as needed.
Click OK to accept the change and close the dialog.