Key name duplicates

I am using the following query to pull meta data from a bucket:
SELECT META(bucket_name) AS Meta FROM bucket_name

when I get my results, I see the keys I want but they are duplicated in the bucket, like so:
Key_name1
Key_name1_0

key_name2
Key_name2_0

Any idea why the keys are adding ’ _0’ to the end of each one?

SDK:PHP

Thanks!