With the last version of JfControls the calculator should be executed as follows:

procedure Calculator; var ANumber: Extended; begin ANumber := 1000; JfCApp.Calculator(2,ANumber); end;

With older versions, you will need to do the following:

procedure Calculator; var ANumber: Double; begin ANumber := 1000; JfCApp.Calculator(2,ANumber); end;

where 2 is the number of decimals.