The DIS hello interval value is derived from the hello interval configured under the interface.
The default IS-IS hello interval is 10 sec. The default DIS hello interval is 10/3 = sec. The default value of the DIS hello interval is not changed. However, if you configure a hello interval of 20 for an interface, then the DIS hello interval for the interface becomes 20/3 =6 sec.
The DIS hello multiplier is the same as the hello multiplier configured under the interface.