vb.net reporting doesnt add up the decimal point

I am using the vb.net reporting provided by mircosoft.

The Database Access has stored a decimal value. 31.23.

in the reporting, it doesn't show 31.00 instead it display 31.23

I use the FormatNumber(Fields!Cubic.Value,2). it display 31.00 not 31.23.

What is the problem with it ? Is it Mircosoft bug.