iPhone Health App - Weight in 'Decimal Stones' not Stones and Pounds

I notice that in the Health App Weight page, I have set 'stones' (st) as the units. My weight today is 12 stone and 8 pounds but the Health app reports this as 12.58 stones. This appears to mean 12 stones and 0.58 of a stone rather than 12 stones and 8 pounds (there being 14 pounds in a stone).

Is there a way to get the Health App Weight to report weight in stones and pounds like all my weight apps (Fitdays, Weight Diary) and Bluetooth scales (HealthKeep FG263LB) do?