numFound changes on changing start and rows

[Rohit]

Hi,

 

We are using Solr3.6 and 2 shards, we are noticing that when we fire a query
with start as 0 and rows X the total numFound and the total numFound changes
when we fire the same exact query with start as y and rows X.

 

For example.

 

First time 

query=abc&start=0&rows=4000

numFound- 56000

 

Second time

query=abc&start=4000&rows=4000

numFound- 55998

 

What can cause this?

 

 

 

Regards,

Rohit