welcome to the forum,
s3 remotes do not support rclone about and are considered unlimited storage.
rclone has no way to know total space, so, rclone just makes up an arbitrary value, 1PiB.
instead, you told rclone to pretend that total space is 100GiB.
do not confuse --vfs-disk-space-total-size with --vfs-cache-max-size
can check out my summary of the two vfs caches