Let me make the question clearer...

A pixel in your pixel has an RGB value, of say, (10,10,10).

If I then darken it by 66%, I might end up with (6,6,6) or (7,7,7) - depending if the integer math rounds up or truncates.

If I then brighten it by 33% I've either got (9,9,9) or (10,10,10).

Thus I'm curious to know if LR uses floating point math for all of its internal operations on pixels before they are presented or integer. This is important because the use of integer means that all brightening operations should be done first because there's a potential loss of information from darkening.

The problem is arguably less relevant for brighter colours.