When using the Filter control and configuring the Fields, if a 'number' type field is used, the value 0 (zero) is ignored, for example:

$("#filter").kendoFilter({
    dataSource: dataSource,
    expressionPreview: true,
    fields: [
      { name: "age", type:"number", defaultValue: 31 },
      {name: "foo", type: "number", defaultValue: 0},
      { name: "name", type:"string", defaultValue: "Rick" }
    ]
  });

'age' and 'foo' are both 'number' type fields, but the default value of 'foo' will be ignored when the filter is chosen in the UI.

Here is a runnable example of this, notice how when selecting 'age' from the fields dropdown, the value correctly defaults to 31, but selecting the 'foo' field will not have the value populate correctly:

https://dojo.telerik.com/eHAROSOz