I've just started experimenting with the Stack Exchange API today.
I created a small wrapper in C#. When I issue a request (e.g. Retrieve a user's profile) I can retrieve the rate limits from the headers (Maximum and Current). I append an API key so my daily limit is 10K instead of 300.

When I execute multiple requests in a row I would expect the current limit (X-RateLimit-Current) to decrement by one for each request until it hits zero.
However, I see that I frequently receive duplicate values.
For example, issuing 10 requests in a row gives me the following results:

Any idea why this is the case? Caching I assume?