If an instrument is a sample, the editor will look like this:
The loop of the sound is shown, and the Start/End values can be moved using the mouse, or changed via the LoopTo/End parameters. The loop can be deactivated by unchecking the Loop? checkbox, but the End parameter remains active in this case: it is possible to have a large sample but only plays a subset of it.
The volume ratio is a handy feature: very often, you will notice that our poor dynamic-less hardware struggle to reproduce soft samples. They need a boost. You can do this with your favorite WAV editor, but but tweaking the volume ratio, the volume is changed in real-time. Plus, this is a non-destructive operation: the sample is not modified so it's easy to reduce the volume if the modified value is wrong.
For the moment, there is no possibility to edit the sample (cut, trim, etc.). This may be done in the future if requested, but AT2 will never aim at being a real sample editor, knowing that excellent editors already exist.