Indexed object names
An object name can refer to a particular occurrence of a data object. The index of the occurrence appears in square brackets immediately after its name. For example, the object name of the third Note would be:
Note[3]
The index between the square brackets can be an integer or the reserved word, "LAST" (a special index value that refers to the last data object of a particular series). The index cannot be another object name. To use a variable index, use the CHOOSE function.
LAST is interpreted in the context in which it is used.