From GridLAB-D Wiki
Integers requiring 16 bits are stored in an int16 built-in data type. An int16 value can represent values between -32,768 to 32,767.
An attempt to store a value outside that range is unpredictable.
GLM
To declare an int16 value in a class use the syntax
class my_class { int16 my_string; }
To define an integer value in an object use the syntax
object my_class { my_integer 123; }
where "value" is a integer within the range of a 16 bit integer.