I believe this is the phone number you want to get the alert on. For me it's the phone number of the phone I have Mobile Admin installed on.
Even though you have Mobile Admin on your phone, I think the alerts for e-mail and for these feeds come from the server itself, so it needs a phone number.
Put in your number and see what happens.
Still figuring mine out, but I think that's your answer.
I've been using the number of the iPhone I have it on and it brings up alerts as a notification on the phone, and then you can go to the App to see what the problem is.
I have noticed, however, that there seems to be a bit of a lag. I'll get the alert before it shows up in mobile admin.