System Generator: How to configure the CORDIC divider block. Understanding the block parameters
The cordic block is split up into a bunch of processing elements (PEs).  Each PE is a bunch of logic operations.  There is some latency associated with each PE already.

You can add additional registers at any point in the pipeline by putting non-zero values into the vector you have highlighted.  The vector should have as many elements as you have requested PEs. In your case, you've requested one PE so it will only look at the first value of the vector, resulting in an additional latency of zero.

As regards notation - [] is standard Matlab for a vector (or matrix, depending on how it's used, but I'll not go into that here!). It's a bit like an array in other languages.

so

a=[5 6 7 8]


creates a 1x4 vector called a.  Element 1 (which you can access in matlab by doing a(1) ) has the value 5.  Element 4 has the value 8.  

Note that Matlab starts its numbering from '1' not '0' like many other languages!