Issue with sending value to XCUIElementTypeSlider via sendKeys()

I’m having an issue while trying to send a value to an XCUIElementTypeSlider object via sendKeys().

Whenever I pass a specific value, the slider gets a value that is somewhat close to the value I passed, but never exact.

For example, if I use the following code snippet:
The second line will print out something like “28%” or “31%”. The values are not what I expect (which would be 30%), and they are also not at all consistent (sometimes over and sometimes under the value I passed).

Has anyone experienced this?

I’m using Appium 1.10.0, iOS 12.1.4, running on an iPhone X.