What does this mean I had checked with HR your application... they had put you on shortlist for September hiring... meaning they put you on first priority... thank you for following up.?

This message indicates that your application has been reviewed by the HR department, and you have been selected as a top candidate for the September hiring process. Being on the shortlist means you are prioritized for potential interviews or further consideration. The sender appreciates your follow-up, suggesting that they value your interest in the position.