Discrepency between n and n

Using the same search request (i.e. show me all results between one year 1 and year 2) and changing the limit gave me the following:

limit=100 0 results found
limit=200 82 results found
limit=300 182 results found

In this case, the limit has a non-intuitive starting value of 117 (i.e. n = 117 + n), and I have found that this value varies. The value is smaller near the start of the data-set.

I have a one-to-many relationship between document and indexed objects, but that's not the cause of this anomaly because I have found the same issue (different starting value) on a test database where the documents are simply indexed.