What does "M" really mean?

[xiaohu2015]

I am very interested LSTM project. But I found that I could not understand the "M" in your blog very well. In your blog, you said that "M" is the total number of memory cells. But I think "M" equals to the time steps. Do note that there are LSTM networks with multiple memory cells. But I think the LSTM network you discussed is comprised of only one memory cell.