Minor discrepancies ERG UI Number spinner control

[BobBooth]

While testing the Release-ready ERG#87 issue, comparing the Settings pane to the index.html with the UI change suggestions, I'm seeing a couple of minor discrepancies, e.g. buttons with lines around them instead of just up/down triangles, text formatted as numeric, not numeric with a % sign after.
Functionally they're about equivalent.

Screenshots

[BobBooth]

Same situation on Configuration page:

[BobBooth]

Comparing Dart and Dark themes, some related issues.

[adgiles]

This is just how the program used by the UI team depicts a number spinner, I don't think they are suggesting we change the default behaviour of the number spinners across the browsers.