The response API generated many answers for one request

Hi OpenAI team,

I found the response API returned many answers for only one requests, especially resent the same question as before. The output_index is from 0 to 19, totally 20 answers for one request. In this situation, it costed huge tokens. My question is how can I limit ChatGPT only return 1 answer (just output_index=0, should not great than 0)

data:{“type”:“response.output_text.delta”,“item_id”:“msg_680dfea6e6408191b3e185c14155a6030e480db67287f954”,“output_index”:19,“content_index”:0,“delta”:“鱼”}

Thanks