Website related question
Hello. This is called a ticker. At the top right hand of your screen there should be 4 icons under your username. Click the 3rd icon that looks like the mountain without the sun. This is suppose to be a graph I think. lol Under this icon you can add your current weight as well as your goal weight. This is also where you'll weigh in and that should update your ticker. Now click manage tickers. Add a new ticker and from here you can design your ticker and edit your settings. Make sure you allow it to show in both your profile and your signature. Your signature is where you are wanting it at the moment. You can also add other things to your signature by going to settings under the little gear icon and going to message board. Hope that helps.
You can't update your old ticker but it can be deleted so that you don't have multiple tickers showing in your signature. Especially when the old one doesn't change. To edit your signature and delete your old ticker, Click the Gear icon in the top right corner of your screen and then click on settings. Now click the Message Board tab. This is where you edit your signature so you can simply click your old ticker and delete it. The sites new tickers will be displayed above the signature if you choose that option in your settings in the 3rd icon under your user name.