Two things jump out at me:
Firstly, A country must have issued your ATPL? ICAO don't issue any, and almost every country on Earth is a signatory to the ICAO. People sometimes seem very reluctant to state the country or authority of issue.
Secondly, why only 300 hours on a 737? There may be a perfectly good reason for this, but in the mind of an interviewer it suggests somebody who has either left their previous job rather quickly, or somebody who has paid for or struggled to come by this very limited experience.
300 hours or 500 hours? There is no particular magic mark, unless a minimum level of experience is required in a companies stipulated requirement. The competition is going to be tough in any event, and you don't really want to be raising "red flags" in your application.