Subscribers is an approximate measure of the number of individuals currently subscribed to your feed.
How is it calculated?
FeedBurner’s subscriber count is based on an approximation of how many times your feed has been requested in a 24-hour period. Subscribers is inferred from an analysis of the many different feed readers and aggregators that retrieve this feed daily. Subscribers is not computed for browsers and bots that access your feed.
Subscribers counts are calculated by matching IP address and feed reader combinations, then using our detailed understanding of the multitude of readers, aggregators, and bots on the market to make additional inferences.
How does it look?
When you select a single day, it looks like this:
This is the number of subscribers to your feed during that day. (It reflects a single point in time and should not be added to the number of subscribers for any other day.)
When you select a date range (like “last 7 days” or “all time”), it looks like this:
This is the average number of subscribers for all of the days selected. This number provides a general understanding of the size of your subscriber base over a time period.