Replica Set (3 Members) backup from operations manager to s3 oplog store is creating lot of oplog slices of very small size instead of 10MB as claimed in documentation(snapshot attached)

Current Behaviour: For three member replica set 60 oplog slices are getting even when no data is being written.

Expected Behaviour: Oplog slice should be atleast 10MB

Ask: Is thier any parameter to set oplog block size to higher value so less number of oplogs slices are generated.

Queries:

1>Does op log size increase with number of replica sets with no change in data?

2>Is their any other way oplog slice numbers being written to S3 can be reduced