Usually, the timer property counts to about 4 decimal places so when it is named Text and displayed, it goes to 4 decimal places. I only want it to 1 decimal place and I also need to find out how to make it go down (e.g. from 10 to 1). Also, how do I get it to start and stop when I want it to.
You could use the property actuator to subtract the Timer’s value from an existing float property that starts at 10.
And for the other one, you just need to attach a script that does some string formating.
Ther timer property is float. So it has more then 4 decimal places. You can round it to as many as you want. You can use it as term in calculation to perform decreasing.
example:
import GameLogic
print 10-round(GameLogic.getCurrentController().owner[“timer”])
Wow, learn something new every day 
Is there an easy way to do this using the user interface rather than Python
The rounding not so much, but the subtraction is easy.
Just put the following into an assign property actuator.
propName1 - propName2
Where propName1 and propName2 are the names of the properties.
It’s the rounding bit I really need though! Any ideas appreciated to start me off. I’m new to BGE