Expected refers to total number of attempts a player can expect to need in order to receive at least one of each drop associated with the respective values. Nearly Guaranteed refers to the total number of attempts a player needs to obtain a 99%, 99.9%, and 99.99% probability to receive at least one of each drop associated with the respective values. For more detailed definitions and information on how these number were obtained, visit here.
Cronus (alternatively Cronos or Kronos) is the youngest of the twelve titans in Greek mythology and father of Zeus, Hades, and Poseidon.
Since Update 7.8 (2013-04-19), the Cronus Blueprint will only be a guaranteed reward the first time Tolstoj is completed and its drop chance exponentially decreases with each repetition. This was put in place to prevent credit farming.
The Cronus was the original melee weapon of the Stalker before update Update 7.11 (2013-05-17).