Sorry about that; there has been some recent trouble between
FeedBurner and Google Feedfetcher that's been ironed out (but we
continue to work with the team on a better long-term solution to
minimize these sorts of reporting gaps). Nothing to adjust on your
end, and don't forget — even if reporting fluctuates for a day or two,
in all likelihood you haven't "lost" any subscribers; it's a matter of
various systems communicating with each other on a regular basis, and
occasionally, when this communication is interrupted, these sorts of
drops can appear.