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