Schema-less indexing search

Question

I have a set of data following a similar data structure below:

{
    "first_name": "some_value",
    "last_name": "some_value_2",
    "instance": "some_instance"
    "num_of_tries": 159,
    "uuid": "some_uuid",
    "background": "something the user can input anything that want here"
    ... more data ...
}

I have a schema-less index using the standard analyzer (no custom mappings).

I pull data from A server that has 52 records. It gets indexed into the index successfully. I then do a match search against the index using the instance field (say, "ins55"). All 52 records come back as expected that match this instance value. I can also see 52 docs, as expected.

I then add another 198 records from B server. It gets indexed into the index successfully. I can see that there are now 250 docs, as expected in the index. I then do match search against the index using the instance field that matches the data from the A server (the "ins55"). Only 22 records come back out of the 52 records that were expected.

Can someone give me some insight into why all 250 docs are listed in the index, but it's not returning the expected number of records for the match?