the same time value return different values，is it a problem

I find the time type accuracy of the database. Using PreparedStatement, the accuracy found out for the sixth time is different from the first five times. This number is exactly the same as the threshold of the PreparedStatement. I can understand that the database can optimize PreparedStatements and reduce repeated parsing and other unnecessary operations. but I don’t quite understand how such processing will affect the execution results(Or maybe I don’t have a deep understanding of PreparedStatement.). now I run the code and get some results；