https://wiki.nxtcrypto.org/wiki/Monetary_System#Currency_Types
Quote
Mintable
If Mintable is checked, three extra fields appear:
MINIMUM DIFFICULTY: The minimum difficulty (minimum 1).
MAXIMUM DIFFICULTY: The maximum difficulty (maximum 255 and greater than the minimum).
ALGORITHM: The hashing algorithm to use. Select SHA256, SHA3, Scrypt, or Keccak25.
A mintable currency is issued with an INITIAL SUPPLY of currency that can increase over time until the TOTAL SUPPLY is reached; thus TOTAL SUPPLY is better named MAXIMUM SUPPLY in this case.
The currency supply is increased through a minting process, governed by the above properties. Minting does not secure the currency as mining does for some other virtual currencies such as Bitcoin; the currency is already secured by the Nxt blockchain and network.
If Mintable is checked, three extra fields appear:
MINIMUM DIFFICULTY: The minimum difficulty (minimum 1).
MAXIMUM DIFFICULTY: The maximum difficulty (maximum 255 and greater than the minimum).
ALGORITHM: The hashing algorithm to use. Select SHA256, SHA3, Scrypt, or Keccak25.
A mintable currency is issued with an INITIAL SUPPLY of currency that can increase over time until the TOTAL SUPPLY is reached; thus TOTAL SUPPLY is better named MAXIMUM SUPPLY in this case.
The currency supply is increased through a minting process, governed by the above properties. Minting does not secure the currency as mining does for some other virtual currencies such as Bitcoin; the currency is already secured by the Nxt blockchain and network.