Appsync GraphQL query does not return all DynamoDB rows?

I have a DynamoDB table and I noticed I was getting inconsistent results (in my web app) as I added more data to the table.
I added 200 test rows to the table. The data includes a date.

I entered 4 rows for a specific date. I can use the DynamoDB console to filter these items and see the 4 records that match the date as expected.

When I issue a GraphQL query in the Appsync console filtered on the same date, I only get 2 items returned.

Hopefully, these images show both the DynamoDB and the Appsync consoles

Any ideas?

Thanks
Kevin