You're right, but also stones are mostly used as an approximate unit of bodyweight in casual conversation, so people would usually say "I'm about 10 and a half stone".

If you're dealing with bodyweight where accuracy matters, like in a medical sense, it's metric anyway. Plenty of people here aren't even sure of how many pounds make up a stone, despite regularly using the latter as a measurement.

I watched a video (Invidious) yesterday detailing the type of coins they used before 1971 in the UK and its empire, and it was actually insane.

1 Pound = 20 Shillings = 240 Pennies, with coins for 0.5, 1, 2, 3, 6 pennies, 1, 2, 2.5, 5 Shillings and banknotes for the Pounds, and each of these coins had 5 or more different names

https://en.wikipedia.org/wiki/£sd