How to "count" the feature detected using SIFT algorithm?

I am using Chenggoju Naveen's code from FileExchange in Matlab, my problem is how can I literally "count" the features detected? Thank you so much!

Here's the link for the code https://www.mathworks.com/matlabcentral/fileexchange/43723-sift--scale-invariant-feature-transform--algorithm . BTW, i am using keypointsdetectingprogram.m script.