This is a gamble, as it can save a lot of time but may also destroy the item as well.
Very fine - This will randomise your item.
Fine - This will upgrade your item, and is what you want the majority of the time.
1:1 - This will change a card from scientist to security, more on this later.
On some servers, this will downgrade a scientist to a D-class On some servers, this option will also kill the player. This is where you place your cards/weapons at the beginning of the process. SCP-914 is one of the most powerful mechanics in the game for one purpose: it upgrades items.