after kafkaTemplate.send(topic, avdlObject); appends dataType in value

Question

I have kafka template and avdl schema. avdl schema format:

recors name{
  union {null, int } a;
  union {null, string} b;
}

now i call kafkaTemplate.send(topic, nameObj); when i try to consume this usig consfluent 5.4 then it return data in format: {a: {"int": "123"}}

why int is appended in the response ?