How to read the gym scales!

I'm just back from an 11 day holiday and eat healthy and calorie counted the full time. I stood on the gym scales today and it said 12:09.2 does this mean 12stone 9 lb or 12stone 9 ounces? I was 12stone 9lb when I left. So that sounds more right but my instructor said it was 9ounces and I'm not sure! Ps before anyone starts I know I am still overweight, hence the reason I'm doing something about it! X