You're reading the documentation for an older, but still supported version (1.33.4).
For information on the latest version, please have a look at 1.33.5.

VARIABLE_TYPE

This enumeration specifies the type of variable to be monitored by the robot controller, and is defined as follows.

Value	Constant Name	Description
0	VARIABLE_TYPE_INSTALL	Installation Variable
1	VARIABLE_TYPE_GLOBAL	Global Variable

Defined in: DRFC.h

typedef enum{
    VARIABLE_TYPE_INSTALL = 0,
    VARIABLE_TYPE_GLOBAL,
} VARIABLE_TYPE;