How to accept only numbers that are < 250?

All this fine but what if , in a numerical field of 3 char I want to accept only numbers < 250 ?

Thanks

Input Masking option is only available for a Text box (short Entry) field. 

If you want to use Input Masking option with a Text Box field that has Numeric validation, you can add a Text field with a custom message to your form and use the conditional logic to show that custom message and hide for example the submit button if the entered number is > 249. You will also have to pass the value from a Text Box field to a Number filed, so that you can use Grater then conditional option. 

How to Pass Field Value to Another Field?

How to Show or Hide Fields Base on User's Answer

Here is my demo form: https://form.jotform.com/72772615179970

Of you can use a Number field and set the Maximum Limit to 249.

Here is a demo form: https://form.jotform.com/72771831979977

Feel free to test and clone my forms.

Let us know if you need further assistance.