Notice that indices start at 1. To access a contiguous range of values in the vector use an index range. Any subset of vector contents may be acquired with an index array containing the indices of the values you want. Everything from it to the end of the line is ignored by glish. If you like, you can load an example of a two-dimensional array of data from a different table that contains a column of spectra.
Glish variables have attributes, a few of which are predefined.
The dimensions of an array are contained in its 'shape' attribute. In this case, there are 33 spectra of 1024 channels each. Back to our 'data' vector, rather than generate an index vector it is more efficient to create a boolean vector with the same number of elements as the 'data' vector and use it as an element mask. Then make a boolean vector of the same length and use it as an index mask to the 'data' vector. The equivalent subarray access could be written without the intermediate 'mask' variable.