NVENC performance issue

My project is to use Quardo K4000 to encode multiple video into h264 streaming. I downloaded nvenc sdk 2.0 from https://developer.nvidia.com/content/nvenc-sdk-zipfile. Several video 1080p yuv files were prepared to test the performance of NVENC on Quardo K4000. I only got around 150 FPS but cannot get 240 FPS which is supposed to reach on NVENC website. I used HP setting.

Thanks for any advice in advance.