Setting 'precision' to 4 means that the digit number after decimal separator is 4. You can override the 'formatter' function to customize your implementation.
<input class="easyui-numberbox" value="1.25" required data-options="
precision:4,
formatter:function(value){
var value = $.fn.numberbox.defaults.formatter.call(this,value);
value = parseFloat(value);
return value;
}">