Follow these steps:

Determine the location of the data to be deleted. It might be a particular directory, file, or database.

Manually deleted the logs from c drive

To manually delete data from disk storage, identify and select the files or folders you want to delete, confirm the deletion, empty the recycle bin or trash folder, and repeat the process as needed.

In Sangfor IAG, you may specify log retention settings to remove logs automatically or manually, alter log levels to limit data logged, and enable log compression to reduce disk space use.

Verify that the data has been deleted by checking the storage usage or searching for the file or directory.

Hi
The IAG has mechanisms to delete the earliest date log automatically when the disk usage reaches 90%.
You doesn't required to worry the disk usage.

Besides, you may also try to adjust the preserved days for the log storage to reduce the disk size.
System -> general -> report center -> Internal report center -> Enable automatically deletion.