The numbers in my fan list don't go up equally as well.
For instance, the numbers go like this:

#1
#2
#3
#5
#7
#9

... etc

I guess it's like this; the number not being displayed anymore is a fan you lost. But the numbers continue as if he's/she's still there, like a 'ghost'.

For instance:

#1 A
#2 B
#3 C
#4 D
#5 E

Are the fans you had last month.
Player D has 'un-fanned' you, so the list still goes like this:

#1 A
#2 B
#3 C
#5 E
#6 F

... etc

This is how your fanlist looks like this month

About your #11 issue, I have no explanation for that, sorry
I hope I cleared it up for you