1. Temporarily change the Location to Below header.
2. You should see some other options – make sure the Inner Navigation Width is set to Contained.
3. Once its set to contained change the Location back to how you had it – and publish those changes.
Its more a foible of how the GP Customizer Logic works – the system removes options that are not applicable when certain conditions are met.
In this case: when the Nav is Floated in the site header, the Nav Width options wouldn’t work so they are removed. This of course does present an issue if they have been changed and the sticky nav is enabled.
Maybe we can take a look at making that more intuitive such as changing the labels for Sticky Navigation when this is the case.