What does `capture_frame_rate` actually do?

Unity Engine
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1

From docs: LLAPI Documentation - Unity ML-Agents Toolkit.

capture_frame_rate: Instructs the simulation to consider time between updates to always be constant, regardless of the actual frame rate.

But in my practice, The lower capture_frame_rate, the FPS higher.

My code:

import time

from mlagents_envs.environment import UnityEnvironment
from mlagents_envs.side_channel.engine_configuration_channel import EngineConfigurationChannel
from mlagents_envs.envs.unity_gym_env import UnityToGymWrapper

channel = EngineConfigurationChannel()
channel.set_configuration_parameters(
    time_scale=1,
    width=320,
    height=180,
    # target_frame_rate=30,
    capture_frame_rate=1,
)
unity_env = UnityEnvironment(file_name="...../AI-Playground.exe", side_channels=[channel])
env = UnityToGymWrapper(unity_env, uint8_visual=True)

obs = env.reset()

start_time = time.perf_counter()
frame_count = 0
fps = 0

while True:
    obs, reward, done, info = env.step([0, 0])
    
    duration = time.perf_counter() - start_time
    frame_count += 1
    if duration >= 1:
        fps = frame_count / duration
        display(fps, clear=True)
        start_time = time.perf_counter()
        frame_count = 0
    
    if done:
        obs = env.reset()