How do I use the Fast Freeze feature and how long does it last?

Activate Fast Freeze by pressing TEMP SETTING until all snowflake positions are illuminated simultaneously; use this feature before adding large amounts of unfrozen food. The freezer will remain in the Fast Freeze setting for 24 hours after the extra-low temperature is reached, then automatically return to the previous temperature setting. For best food quality, do not exceed 3 lbs (1,361 g) per cubic foot (28.32 L) of freezer space. (Page 7)