Hi Tiffany,
Thanks for the reply. The resolution of the recording is not directly related to the length of the meeting, it is affected by the resolution of the video and the network bandwidth. One possible way to increase the recording quality would be enabling the Group HD in your account setting: https://support.zoom.us/hc/en-us/articles/207347086-Group-HD.
For Client SDK, we do not have any interfaces or ways to change the resolution of recording.
Hope this helps. Thanks!