apple health saying 12.12 stone is less than 12.9 stone

So I’m monitoring my weight loss in stone as this is my preferred measurement however when I go from 12 stone 12lb (typing 12.12) to 12st 9lb (typing 12.9) it’s showing I have gained weight.

i understand this is as it’s working as a maths decimal but is there a way to get this to work better other than changing my weight unit?