SORT COLUMN NUMBER

Hello,

I have this code for a column:

{                            
                "mData": "credito_restante",                
                "sDefaultContent": "",
                "bSortable": true,
                "mRender": function (val, type, row) {                                                            
                    
                    var sReturn = "<strong style='color:purple'>" + val + "</strong>";                                                                           
                    return sReturn;
                }
 },

But when I sort by this column, it sorts as a text, not as a number.
I try this:

sType: numeric

But not works, Any idea please??

Thank you!