To control the decimal point in real value do the following :

1- right click on the real field and choose properties

2- go to NoOfDecimals property and put any number you want for example (1 or 2 or 3)

This means the numbers after the decimal point  example :

 if the value is 2.31689

if you put 1 the result is 2.3

if you put 2 the result is 2.31