Incorrect behaviors of the right side slider

[nicoddemus]

Hi!

First of all, thanks a lot for the awesome control!

I noticed two incorrect behaviors on the right handle:

1. If you click on it (press + release), it immediately jumps 1 step to the left.
2. If you click on the right of the handle, instead of it moving 1 step to the right, it actually moves 1 step to the left.

Here's a GIF demonstrating the problem:

I will open a PR with a fix shortly.