With MDF: the displayed value is used

Again, press 5, , 9, , and : 0.6. Press and the 0 key: . The value becomes exactly 0.6, shown as $\displaystyle \dfrac{3}{5}$. Press , type 9, and press : $\displaystyle 5\dfrac{2}{5}$. , and again, shows 5.4. Finally, pressing , , , and returns to the normal number format. The display still shows 5.4.