The default setting (unchecked) considers only the worst-case device selected at compile time and optimizes to meet timing requirements.
By enabling (checking) this option, both the worst and fastest values are considered, so the timing margin for the hold time is also optimized.
 
The setting method is to check "Yes/No" in the "Optimaze Fast-Corner Timing" dialog Box in the Quartus II pull-down menu Assignments ⇒ Settings ⇒ Fitting.
 
For details, refer to the Quartus II HELP using the following method.
From the Quartus II pull-down menu, HELP ⇒ Index ⇒ Search word ”Settings Dialog Box” ⇒ Fitter Settings ⇒ Timing-driven Compilation