Doesn't matter how it's partitioned. You still need to use advanced size check.
You should notice that HDTach's list of drives is only hardware drives, it lumps all the partitions under a single hard drive, you're not testing just that partition if you're somehow saying you don't need advanced size check and that's why it's showing ~8gb.
If you enable advanced size check, the graph will be for the whole drive no matter how it's partitioned.