AngularJS and cam-variable-type doesn't work

Hello all,

the following section describes how to use the cam-variable-type directive as a validation directive (Controls | docs.camunda.org

I want to create a field that checks if the entered value is in the specified range from 1 to 500.

<div class="form-group">
			<label for="customerId-field">Kostenbetrag</label>
			<input required
				   type="number" 
				   name="size"
				   cam-variable-name="SIZE"
				   cam-variable-type="number"
				   min="1" 
				   max="500"/>{{size}}</label><br />
			<span ng-show="form.size.$error.camVariableType">The value is not valid</span>
			<span ng-show="form.size.$error.min || form.size.$error.max">
			  The value must be in range 1 to 500!</span>
		  </div>

Unfortunately, an error message comes up even though the number is in the range. Does anyone know what is causing this?

image

Thanks in advance for help.