It is my understanding that you want to know about the number of columns in the output matrix returned by extractLBPFeatures function.
The extractLBPFeatures function computes uniform local binary patterns for grayscale image. By default, the function uses 8 neighbours (P = 8), and it does not encode rotation information, i.e., Upright argument is set to true.
By default, the number of output bins are (P×P-1)+3. For P = 8, this value is (8×7)+3 = 59. So, the number 59 represents the number of bins in the LBP histogram.
Hope this helps!