Not really sure how your gui should look like, but to change Int numbers you could use stepper or slider (range of numbers).
When using a textfield for any random number input you should have a look for the textfield filter function, which can allow or deny what ever you need in a textfield (e.g. only numbers allowed).
When using a textfield for any random number input you should have a look for the textfield filter function, which can allow or deny what ever you need in a textfield (e.g. only numbers allowed).