Subscription Stats jumping up and down

[ffscambridge]

I use Feedburner for RSS feeds and Feedblitz for e-mail
subscriptions. I have had about 65 Feedblitz subscribers for the past
month and a dozen Google reader subscribers; the number has not
changed much.

In the Feed Stats dashboard, the number of subscriber shown runs at
70+ for a few days, then drops below ten for a few days, then jumps up
again. This has been going on for a few weeks, even though the number
of subscribers has barely changed. Why does the number keep bouncing
around?

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