I need a little help interpreting my yDNA results.

Of the members in my surnname project that are R1b1a2 (there are a few "I"s in there):
At DYS19 fourteen members are 14 and seven (including myself) are 15.
At DYS391 two members (including myself) are 10 and nineteen are 11.

I am the ONLY member that is 15/10 for these two markers.

Three of us (including myself) have tested DF21+. One is 14/11, one is 15/11 and one is 15/10.

So, what does it all mean???